Composite bodies and methods for making same

ABSTRACT

This invention relates generally to a novel directed metal oxidation process which is utilized to produce self-supporting bodies. In some of the more specific aspects of the invention, a parent metal (e.g., a parent metal vapor) is induced to react with at least one solid oxidant-containing material to result in the directed growth of a reaction product which is formed from a reaction between the parent metal and the solid oxidant-containing material. The inventive process can be utilized to form bodies having substantially homogeneous compositions, graded compositions, and macrocomposite bodies.

TECHNICAL FIELD

This invention relates generally to a novel directed metal oxidationprocess which is utilized to produce self-supporting bodies. In some ofthe more specific aspects of the invention, a parent metal (e.g., aparent metal vapor) is induced to react with at least one solidoxidant-containing material to result in the directed growth of areaction product which is formed from a reaction between the parentmetal and the solid oxidant-containing material. The inventive processcan be utilized to form bodies having substantially homogeneouscompositions, graded compositions, and macrocomposite bodies.

BACKGROUND ART

In recent years, there has been an increasing interest in the use ofceramics for structural applications historically served by metals. Theimpetus for this interest has been the relative superiority of ceramics,when compared to metals, with respect to certain properties, such ascorrosion resistance, hardness, wear resistance, modulus of elasticityand refractory capabilities.

However, a major limitation on the use of ceramics for such purposes isthe feasibility and cost of producing the desired ceramic structures.For example, the production of metal boride and metal carbide bodies bythe methods of hot pressing, reaction sintering, and reaction hotpressing is well known. While there has been some limited success inproducing metal boride and metal carbide bodies according to theabove-discussed methods, there is still a need for a more effective andeconomical method to prepare such bodies.

In addition, a second major limitation on the use of ceramics forstructural applications is that ceramics generally exhibit a lack oftoughness (i.e., damage tolerance, or resistance to fracture). Such lackof toughness tends to result in sudden, easily induced, catastrophicfailure of ceramics in applications involving rather moderate tensilestresses. This lack of toughness tends to be particularly common inmonolithic ceramic bodies.

One approach to overcome the above-discussed problem has been theattempt to use ceramics in combination with metals, for example, ascermets or metal matrix composites. The objective of this known approachis to obtain a combination of the best properties of the ceramic (e.g.,hardness and/or stiffness) and the best properties of the metal (e.g.,ductility). While there has been some general success in the cermet areain the production of boride compounds, there still remains a need formore effective and economical methods to prepare dense boride-containingmaterials.

Moreover, there also has been significant interest in modifying theproperties of known or existing materials in a manner which renders thematerials suitable for use in environments which normally wouldadversely affect such materials. For example, one such modifyingapproach generally relates to coating onto a surface of a substratematerial a second material, which has properties which differ from theunderlying substrate material.

Various methods exist for coating substrate materials. A first categoryof coating processes is generally referred to as overlay coatings.Overlay coatings involve, typically, a physical deposition of a coatingmaterial onto a substrate. The coating material typically enhances theperformance of the substrate by, for example, increasing the erosionresistance, corrosion resistance, high temperature strength, etc., ofthe substrate material. These overlay coatings typically result in thesubstrate material having longer life and/or permit the use of thesubstrate material in a number of environments which normally mightadversely affect and/or destroy the utility of the substrate materialabsent the placement of the overlay coating thereon.

Commonly utilized overlay coating methods include Chemical VaporDeposition, Hot Spraying, Physical Vapor Deposition, etc. Briefly,Chemical Vapor Deposition utilizes a chemical process which occursbetween gaseous compounds when such compounds are heated. Chemical VaporDeposition will occur so long as the chemical reaction produces a solidmaterial which is the product of the reaction between or in the gaseouscompounds. The Chemical Vapor Deposition process is typically carriedout in a reaction chamber into which both a reactive gas and a carriergas are introduced. A substrate material is placed into contact with thereactant and carrier gases so that reaction between the gases anddeposition of the reaction solid will occur on the surface of thesubstrate. Chemical Vapor Deposition processes typically involve the useof corrosive alkali gases (e.g., chlorides, fluorides, etc.) in thereaction chamber which must be carefully handled. Accordingly, eventhough Chemical Vapor Deposition processes may produce desirablecoatings on some materials, the equipment that is utilized typically iscomplicated in design and is expensive to operate.

A number of Hot Spraying techniques also exists for the placement of anoverlay coating on a substrate material. The three most widely utilizedHot Spraying techniques include Flame Spraying, Plasma Spraying, andDetonation Coating.

Flame Spraying utilizes a fine powder which is contained in a gaseousstream and which is passed through a combustion flame which renders thefine powder molten. The molten powder is then caused to impinge on asurface of a substrate material which is to be coated, which istypically cold relative to the flame spray. Bonding of the coating offlame-sprayed material to the substrate is primarily of a mechanicalnature. The flame-sprayed coating is usually not fully dense and thus isoften subsequently treated by a fusing operation to densify the coating.

Plasma Spraying is somewhat similar to Flame Spraying, except that thefine powder, instead of being passed through an intense combustionflame, is passed through an electrical plasma which is produced by a lowvoltage, high current electrical discharge. As a result, disassociationand ionization of gases occur which results in a high temperatureplasma. The high temperature plasma is directed toward a substratematerial resulting in the deposition of a layer of coating material onthe substrate.

Detonation Coating is a process which has some similarities to FlameSpraying, except that a desired amount of powder is directed at highvelocity (e.g., about 800 meters per second) toward the surface of asubstrate material which is to be coated. While the particles are beingaccelerated in a hot gas stream, the particles melt. Moreover, the highkinetic energy of the particles when impinging on the surface of asubstrate material results in additional heat being generated, therebyassisting the coating process.

The third category of so-called overlay coatings is Physical VaporDeposition coatings. Physical Vapor Deposition coatings include, forexample, Ion Sputtering, Ion Plating, and Thermal Evaporation.

In Ion Sputtering, a vacuum,chamber houses a cathode electrode such thatthe cathode electrode emits atoms and atomic clusters toward a substratematerial to result in a sputtered film or coating being deposited on thesubstrate.

Ion Plating of a substrate material involves the use of a heated metalsource which emits metal atoms toward a substrate material which is tobe coated. Specifically, an electron beam is typically utilized toexcite the metal atoms from the metal source. The excited metal atomsare then directed toward the substrate material to be coated.

Thermal Evaporation also relies on the excitation of atoms from a metalsource. Specifically, in a vacuum chamber, a metal source is heated sothat metal atoms evaporate from the metal source and are directed towarda substrate material to be coated. The metal atoms then collect as acoating on the substrate.

A second general category of coating formation techniques is known asconversion coating techniques. In conversion coating techniques, asubstrate material, typically, is involved in a chemical reaction whichmodifies the composition and/or microstructure of the surface of thesubstrate. These conversion coating techniques also can result indesirable surface modification of substrate materials. Typical examplesof conversion coating techniques include Pack Cementation and SlurryCementation.

Pack Cementation and Slurry Cementation utilize diffusion of one or morematerials to form a surface coating. Specifically, in each of theseprocesses, a substrate material is contacted with a metal sourcematerial such that a metal from the metal source material may diffuseinto the substrate material and/or a component of the substrate materialmay diffuse toward the metal source material. Specifically, for example,in Pack Cementation, a substrate material is buried within a powdermixture which comprises, typically, both a metal which is to react withthe substrate material and an inert material. A carrier gas is theninduced to flow into the powder mixture so that the carrier gas cancarry metal atoms from the metal powder to the surface of the substrateand deposit the metal atoms thereon. Both Pack Cementation and SlurryCementation typically occur in a retort or vacuum furnace and thecarrier gas is free to transport metal atoms from the metal powder tothe surface of the substrate material. Typical carrier gases include thehalogen gases. Many different approaches to Pack Cementation have beenmade, however, most of these approaches utilize the above-discussedsteps.

Slurry Cementation is quite similar to Pack Cementation, however, inSlurry Cementation, a composition typically is coated onto a surface ofa substrate material prior to conducting the diffusion process in avacuum or retort furnace. In each of Pack Cementation and SlurryCementation, the temperature of reaction is typically elevated to permitthe metal atoms to react with the substrate by solid state diffusionwhich results in the formation of a coating material.

The above-discussed coating techniques have been briefly addressedherein to give the reader a general understanding of the art. However,it should be understood that many specific variations to theabove-discussed techniques exist. Specifically, each of the coatingprocesses discussed above has been discussed in detail in a number ofreadily available sources, including textbooks, conference proceedings,and patents. For further information relating to the detail of theseprocesses, the reader is encouraged to consult the literature referredto above. However, even from the brief discussions above, it is clearthat each of the techniques suffers from various limitations. Forexample, in the overlay coating techniques, the physical deposition of acoating onto a substrate material does not insure an acceptableinterface between the substrate and the coating. Specifically, becausemost of the overlay coating techniques simply rely on the use of aphysical bonding between the coating and the substrate, the coating maynot adhere to the substrate in a desirable manner. Accordingly, thepurpose of the coating may be compromised completely. Additionally,almost all of the overlay coating processes depend on the use ofsomewhat complex deposition equipment. For example, Chemical VaporDeposition requires the use of complicated control means for controllingthe rate of flow of reactive and carrier gases in a reaction chamber,the ability to handle corrosive alkali gases (e.g., fluorides andchlorides). Accordingly, the equipment utilized for Chemical VaporDeposition is typically quite expensive.

Moreover, with regard to the so-called conversion coating techniqueswhich are formed by, for example, Pack Cementation and SlurryCementation techniques, the coatings which result on substrate materialsmay not be uniform due to the inclusion of solid materials or porositywhich result from exposure of the substrate to either or both the powdermetal source and/or inert materials utilized in the Pack Cementation orSlurry Cementation processes. Still further, many of the PackCementation and Slurry Cementation techniques may require the use ofsomewhat complex equipment.

The present invention is a significant improvement over all known priorart techniques in that relatively simple equipment can be utilized toachieve a virtually infinite combination of desirable bodies.Specifically, the present invention permits the formation of a coatingon substrate materials or the creation of new materials from, forexample, solid oxidant precursor materials. The coatings which form arevery dense and are substantially uniform in thickness. Additionally, thecoatings can be applied in thicknesses heretofore believed difficult, ifnot impossible, to achieve. Moreover, due to the simplicity of theprocess and, for example, the rate of conversion of a solid oxidantmaterial to a reaction product, entire solid oxidant bodies can beconverted from one composition to another. These and other aspects ofthe invention will become apparent to those skilled in the art whenreading the following sections.

Discussion of Commonly Owned U.S. Patents and Patent Applications

This application is a Continuation-in-Part of U.S. patent applicationSer. No. 07/543,316, filed Jun. 25, 1990, in the names of Terry DennisClaar et al., and entitled "Methods For Making Self-Supporting Compositebodies and Articles Produced Thereby," the subject matter of which isexpressly incorporated herein by reference.

A directed metal oxidation reaction is disclosed in U.S. Pat. No.4,713,360, which issued on Dec. 15, 1987, and is entitled "Novel CeramicMaterials and Methods for Making Same" and which was issued in the namesof Marc S. Newkirk et al. This patent discloses that a molten parentmetal can react with a vapor-phase oxidant and result in the directedgrowth of an oxidation reaction product.

A similar directed metal oxidation reaction process is disclosed in U.S.Pat. No. 4,851,375, which issued on Jul. 25, 1989, and is entitled"Methods of Making Composite Ceramic Articles Having Embedded Filler",and which issued in the names of Marc S. Newkirk et al. This patentdiscloses that a molten parent metal can react with an oxidant to growoxidation-reaction product into a substantially inert filler material,thereby forming a ceramic matrix composite body.

The reactive infiltration into a bed or mass comprising boron carbide isdiscussed in co-pending U.S. patent application Ser. No. 07/446,433,filed in the names of Terry Dennis Claar et al., on Dec. 5, 1989, andentitled "A Process For Preparing Self-Supporting Bodies and ProductsProduced Thereby", which is a continuation of U.S. Pat. No. 4,885,130,which issued on Dec. 5, 1989, in the names of Terry Dennis Claar et al.,and is entitled "Process For Preparing Self-Supporting Bodies andProducts Produced Thereby", which in turn is a Continuation-In-Partapplication of U.S. patent application Ser. No. 07/137,044, filed onDec. 23, 1987, in the names of Terry Dennis Claar et al., and entitled"Process For Preparing Self-Supporting Bodies and Products Made Thereby,and which was allowed on Jan. 2, 1990, which in turn is aContinuation-In-Part application of U.S. patent application Ser. No.07/073,533, filed in the names of Danny R. White, Michael K. Aghajanianand T. Dennis Claar, on Jul. 15, 1987, and entitled "Process forPreparing Self-Supporting Bodies and Products Made Thereby".

Briefly summarizing the disclosure contained in each of theabove-identified patent applications and issued Patent relating toreactive infiltration, self-supporting ceramic bodies are produced byutilizing a parent metal infiltration and reaction process (i.e.,reactive infiltration) in the presence of a mass comprising boroncarbide. Particularly, a bed or mass comprising boron carbide isinfiltrated by molten parent metal, and the bed may be comprisedentirely of boron carbide, thus resulting in a self-supporting bodycomprising one or more parent metal boron-containing compounds, whichcompounds include a parent metal boride or a parent metal boron carbide,or both, and typically also may include a parent metal carbide. It isalso disclosed that the mass of boron carbide which is to be infiltratedmay also contain one or more inert fillers mixed with the boron carbide.Accordingly, by combining an inert filler, the result will be acomposite body having a matrix produced by the reactive infiltration ofthe parent metal, said matrix comprising at least one boron-containingcompound, and the matrix may also include a parent metal carbide, thematrix embedding the inert filler. It is further noted that the finalcomposite body product in either of the above-discussed embodiments(i.e., filler or no filler) may include a residual metal as at least onemetallic constituent of the original parent metal.

Broadly, in the disclosed method of each of the above-identifiedreactive infiltration patent applications and issued Patent, a masscomprising boron carbide is placed adjacent to or in contact with a bodyof molten metal or metal alloy, which is melted in a substantially inertenvironment within a-particular temperature envelope. The molten metalinfiltrates the boron carbide mass and reacts with the boron carbide toform at least one reaction product. The boron carbide is reducible, atleast in part, by the molten parent metal, thereby forming the parentmetal boron-containing compound (e.g., a parent metal boride and/orboron compound under the temperature conditions of the process).Typically, a parent metal carbide is also produced, and in certaincases, a parent metal boro carbide is produced. At least a portion ofthe reaction product is maintained in contact with the metal, and moltenmetal is drawn or transported toward the unreacted boron carbide by awicking or a capillary action. This transported metal forms additionalparent metal, boride, carbide, and/or boron carbide and the formation ordevelopment of a ceramic body is continued until either the parent metalor boron carbide has been consumed, or until the reaction temperature isaltered to be outside of the reaction temperature envelope. Theresulting structure comprises one or more of a parent metal boride, aparent metal boron compound, a parent metal carbide, a metal (which, asdiscussed in each of the above-identified patent applications and issuedPatent, is intended to include alloys and intermetallics), or voids, orany combination thereof. Moreover, these several phases may or may notbe interconnected in one or more dimensions throughout the body. Thefinal volume fractions of the boron-containing compounds (i.e., borideand boron compounds), carbon-containing compounds, and metallic phases,and the degree of interconnectivity, can be controlled by changing oneor more conditions, such as the initial density of the boron carbidebody, the relative amounts of boron carbide and parent metal, alloys ofthe parent metal, dilution of the boron carbide with a filler,temperature, and time. Preferably, conversion of the boron carbide tothe parent metal boride, parent metal boron compound(s) and parent metalcarbide is at least about 50%, and most preferably at least about 90%.

The typical environment or atmosphere which was utilized in each of theabove-identified patent applications and issued Patent was one which isrelatively inert or unreactive under the process conditions.Particularly, it was disclosed that an argon gas, or a vacuum, forexample, would be suitable process atmospheres. Still further, it wasdisclosed that when zirconium was used as the parent metal, theresulting composite comprised Zirconium diboride, zirconium carbide, andresidual zirconium metal. It was also disclosed that when aluminumparent metal was used with the process, the result was an aluminum borocarbide such as Al₃ B₄₈ C₂, AlB₁₂ C₂ and/or AlB₂₄ C₄, with aluminumparent metal and other unreacted unoxidized constituents of the parentmetal remaining. Other parent metals which were disclosed as beingsuitable for use with the processing conditions included silicon,titanium, hafnium, lanthanum, iron, calcium, vanadium, niobium,magnesium, and beryllium.

Moreover, co-pending U.S. patent application Ser. No. 07/137,044(discussed above and hereinafter referred to as "application Ser. No.'044"), discloses that in some cases it may be desirable to add a carbondonor material (i.e., a carbon-containing compound) to the bed or masscomprising boron carbide which is to be infiltrated by molten parentmetal. Specifically, it was disclosed that the carbon donor materialcould be capable of reacting with the parent metal to form a parentmetal-carbide phase which could modify resultant mechanical propertiesof the composite body, relative to a composite body which was producedwithout the use of a carbon donor material. Accordingly, it wasdisclosed that reactant concentrations and process conditions could bealtered or controlled to yield a body containing varying volume percentsof ceramic compounds, metal and/or porosity. For example, by adding acarbon donor material (e.g., graphite powder or carbon black) to themass of boron carbide, the ratio of parent metal-boride/parentmetal-carbide could be adjusted. In particular, if zirconium was used asthe parent metal, the ratio of ZrB₂ /ZrC could be reduced (i.e., moreZrC could be produced due to the addition of a carbon donor material inthe mass of boron carbide).

Still further, Issued U.S. Pat. No. 4,885,130 (discussed above andhereinafter referred to as "Pat. No. '130"), discloses that in somecases it may be desirable to add a boron donor material (e.g., aboron-containing compound) to a bed or mass of boron carbide which is tobe infiltrated by molten parent metal. The added boron-containingcompound can then behave in a manner similar to the carbon-containingcompound discussed above in relation to application Ser. No. '044,except that the ratio of ZrB₂ /ZrC could be increased, as opposed toreduced.

Still further, U.S. Pat. No. 4,904,446, which issued on Feb. 27, 1990,in the names of Danny Ray White and Terry Dennis Claar and entitled"Process For Preparing Self-Supporting Bodies and Products MadeThereby", discloses that a parent metal can react with a mass comprisingboron nitride to result in a body comprising a boron-containingcompound, a nitrogen-containing compound and, if desired, a metal. Themass comprising boron nitride may also contain one or more inertfillers. Relative amounts of reactants and process conditions may bealtered or controlled to yield a body containing a varying volumepercents of ceramic, metal and/or porosity.

Moreover, co-pending U.S. patent application Ser. No. 07/296,961, whichwas filed on Jan. 13, 1989, in the names of Terry Dennis Claar et al.,and entitled "A Process for Preparing Self-Supporting Bodies HavingControlled Porosity and Graded Properties and Products ProducedThereby", and which was allowed on Feb. 27, 1990, discloses that apowdered parent metal can be mixed with a bed or mass comprising boroncarbide and, optionally, one or more inert fillers, to form aself-supporting body. The application also discloses that the propertiesof a composite body can be modified by, for example, tailoring theporosity by appropriate selection of the size and/or composition of theparent metal powder or particulate, etc., which is mixed with the boroncarbide.

The disclosures of each of the above-discussed Commonly Owned U.S.patents' and U.S. patent applications are herein expressly incorporatedby reference.

SUMMARY OF THE INVENTION

In accordance with the present invention, there are provided a pluralityof methods for producing self-supporting bodies. Specifically, in onepreferred embodiment of the invention at least one vapor-phase parentmetal is caused to react with at least one solid oxidant-containingmaterial to form at least one reaction product.

In all embodiments of the invention, the following processing steps areutilized. A material, at least a portion of which comprises a solidoxidant, is placed into a reaction chamber. The reaction chamber shouldbe made of, or at least coated with, a material which does not adverselyreact with any of the materials utilized in the process of the presentinvention. Moreover, the reaction chamber should be capable of isolatingall materials contained therein from any external contaminants whichmight adversely impact the process of the present invention. Avapor-phase parent metal source is contained within the reaction chamberin a manner which permits an interaction between the parent metal vaporand the solid oxidant-containing material. The parent metal vapor can beintroduced by providing a solid source of parent metal within thereaction chamber, or contiguous to the reaction chamber, and heating thesolid source of parent metal until a temperature is achieved whichresults in an adequate vapor pressure of the parent metal being presentin the reaction chamber. The parent metal vapor should be capable ofcontacting that portion of the solid oxidant-containing material whichis to react with the parent metal vapor. Accordingly, only a portion ofa solid oxidant-containing material may be exposed to the parent metalvapor to create a reaction product or alternatively, substantially allof a solid oxidant-containing material can be exposed to a parent metalvapor to create reaction product.

The solid oxidant-containing material which is to react with the parentmetal vapor should be, or contain, a material which is itself capable ofreacting with the parent metal vapor to form reaction product, or shouldbe capable of being coated with a material which contains a solidoxidant which is capable of forming a desirable reaction product whencontacted with a parent metal vapor.

In a first preferred embodiment of the invention, a solidoxidant-containing material is comprised substantially completely ofsolid oxidant which is capable of reacting with parent metal vapor underthe process conditions of the invention. Accordingly, for example, acarbonaceous material is placed within a reaction chamber and is placedinto contact with parent metal vapor (e.g., titanium, hafnium,zirconium, silicon and/or niobium) to result in the formation of aparent metal carbide reaction product. The amount of reaction productthat can form includes: (1) a relatively thin layer of reaction productformed upon a carbonaceous substrate material, (2) a relatively thicklayer of reaction product formed upon a carbonaceous substrate material,or (3) substantially complete conversion of the substrate material toreaction product.

In a second preferred embodiment of the invention, a composite materialcan be formed. Specifically, a solid oxidant substrate is first coatedwith a substantially inert filler material prior to being exposed to aparent metal vapor. A reaction product of parent metal vapor and solidoxidant is then formed and the substantially inert filler material isthereafter embedded in the formed reaction product, thereby forming acomposite material. The filler material may comprise any particularshape or combination of shapes of filler material, and may have anysuitable chemical constituency. However, the filler material should bechosen so as to be capable of surviving the process of the presentinvention. Moreover, by appropriate selection of filler material(s) tobe embedded by reaction product, a wide range of desirable propertiescan be achieved.

In a third preferred embodiment of the invention, a solidoxidant-containing substrate material is first coated or contacted withat least one material which will react with at least one other materialexternal to the solid oxidant (e.g., in the coating), and/or react withat least one material in the solid oxidant-containing material and/or,react with the parent metal vapor. For example, a powdered parent metalhaving a substantially similar or substantially different compositionfrom the parent metal vapor, may be first placed as a coating onto atleast a portion of a surface of a solid oxidant-containing materialprior to the parent metal vapor contacting the solid oxidant-containingmaterial. Reactions may then occur between the powdered parent metal onthe surface of the solid oxidant-containing material and the solidoxidant itself and/or reactions may occur between the powdered parentmetal on the solid oxidant-containing material and the parent metalvapor. Additionally, at least one solid oxidant (e.g., boron carbide)which is different in composition from the solid oxidant-containingsubstrate material (e.g., carbon) may be placed onto the surface of thesolid oxidant-containing material prior to contacting the parent metalvapor with the solid oxidant-containing material. The different solidoxidant placed on the surface of a solid oxidant-containing materialsubstrate should be capable of reacting with the parent metal vapor toresult in a reaction product which may be different from the reactionproduct which results when the parent metal vapor reacts with thesubstrate solid oxidant-containing material. This different reactionproduct could serve as a filler material. Still further, a powderedparent metal (e.g., titanium, hafnium, and/or zirconium) having asubstantially similar or substantially different chemical compositionfrom the parent metal vapor (e.g., titanium, hafnium, and/or zirconium)may be mixed with a solid oxidant powder which is different incomposition from the solid oxidant-containing material substrate topermit the formation of a reaction product which is different than thereaction product which forms when the parent metal vapor contacts thesubstrate solid oxidant-containing material. This different reactionproduct could also serve as a filler material. Further, if more than onereaction product is formed, it is possible that the reaction productsmay also react with each other.

In a fourth preferred embodiment of the invention, each of the first andthird embodiments discussed above can be expanded on by positioning afiller material on at least a portion of the surface of the solidoxidant-containing material. Accordingly, the filler material could beuniformly or non-homogeneously mixed with, for example, a powderedparent metal of substantially similar or substantially differentcomposition than the vapor-phase parent metal. Moreover, the fillermaterial could be mixed in a substantially uniform or non-homogeneousmanner with a solid oxidant powder which is placed onto the surface of asolid oxidant-containing substrate material. Still further, a fillermaterial may be mixed either substantially uniformly ornon-homogeneously with the combination of a parent metal powder (havinga substantially similar or substantially different composition than aparent metal vapor) and a solid oxidant.

In a fifth preferred embodiment of the invention, a solidoxidant-containing material is placed as a coating on a substratematerial which normally would not react with a parent metal vapor so asto permit the formation of a reaction product coating having acomposition different than the solid oxidant-containing material coatingand the substrate material.

Further, in each of the above-discussed embodiments, it is possible tosupply substantially simultaneously more than one parent metal vapor topermit the formation of an even greater number of reaction products andpossible interactions between forming or formed reaction products.

It should be understood that a large number of combinations of parentmetal vapors, solid oxidant-containing materials, solid oxidant powders,parent metal powders, fillers, etc., are possible for utilization inaccordance with the teachings of the present invention. Thus, whileevery potential combination of materials has not been expresslydiscussed above herein, such combinations should readily occur to thoseskilled in the art.

DEFINITIONS

As used herein in the specification and the appended claims, the termsbelow are defined as follows:

"Different" as used herein in conjunction with chemical compositions,means that a primary chemical constituent of one material differs from aprimary chemical constituent of another referenced material.

"Filler"as used herein, means either single constituents or mixtures ofconstituents which are substantially non-reactive with, and/or oflimited solubility in, parent metal powders and/or parent metal vaporsand may be single or multi-phase. Fillers may be provided in a widevariety of forms such as powders, flakes, platelets, microspheres,whiskers, bubbles, etc., and may be dense or porous. "Fillers" may alsoinclude ceramic fillers, such as alumina or silicon carbide, as fibers,particulates, whiskers, bubbles, spheres, fibermats, or the like, andceramic-coated fillers such as carbon fibers coated with alumina orsilicon carbide to protect the carbon from attack. "Fillers" may alsoinclude metals. "Fillers" should also be capable of surviving theprocessing conditions.

"Parent Metal Powder" as used herein, means that metal (e.g., zirconium,titanium, hafnium, silicon, niobium, etc.) which is the precursor for areaction product of the powdered parent metal and a solid oxidant (e.g.,parent metal carbides, etc.) and includes that metal as a pure orrelatively pure metal, a commercially available metal having impuritiesand/or alloying constituents therein and an alloy in which that metalprecursor is the major constituent. When a specific metal is mentionedas the powdered parent metal, the metal identified should be read withthis definition in mind unless indicated otherwise by the context.

"Parent Metal Vapor" or "Vapor-Phase Parent Metal" as used herein, meansthat metal (e.g., zirconium, titanium, hafnium, silicon, niobium, etc.)which is the vapor-phase precursor for the reaction product (e.g.,parent metal carbides, etc.) of the parent metal and a solid oxidant andincludes that metal as a pure or relatively pure metal, a commerciallyavailable metal having impurities and/or alloying constituents thereinand an alloy in which that metal precursor is the major constituent.When a specific metal is mentioned as the parent metal vapor, the metalidentified should be read with this definition in mind unless indicatedotherwise by the context.

"Parent Metal Boride" and "Parent Metal Boro Compounds" as used herein,means a reaction product containing boron formed upon reaction between aboron source material and at least one parent metal source (eithervapor-phase or solid phase) and includes a binary compound of boron withthe parent metal, as well as ternary or higher order compounds.

"Parent Metal Carbide" as used herein, means a reaction productcontaining carbon formed upon reaction of a solid oxidant carbon sourceand a parent metal.

"Parent Metal Nitride" as used herein, means a reaction productcontaining nitrogen formed upon reaction of a nitrogen source (e.g.,boron nitride) and a parent metal.

"Reaction Product" as used herein, means the product which forms as aresult of the reaction between a parent metal and a solid oxidant.

"Solid Oxidant" as used herein, means an oxidant in which the identifiedsolid is the sole, predominant, or at least a significant oxidizer ofthe parent metal under the conditions of the process.

"Solid Oxidant-Containing Material" as used herein, means a materialwhich contains a solid oxidant. The solid oxidant may comprisesubstantially all of the material or may comprise only a portion of thematerial. The solid oxidant may be substantially homogeneously orheterogeneously located within the material.

"Solid Oxidant Powder" as used herein, means an oxidant in which theidentified solid is the sole, predominant, or at least a significantoxidizer of a parent metal powder and/or parent metal vapor and which islocated on at least a portion of a surface of another material (e.g., asolid oxidant-containing material).

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic cross-sectional view of an assembly utilized toproduce a body in accordance with the present invention;

FIG. 2a is a photomicrograph taken at 400× of a sample made inaccordance with Example 1;

FIG. 2b corresponds to a fractograph taken at 200× corresponding tofractured sample made in accordance with Example 1;

FIG. 3 comprises a schematic cross-sectional view of an assemblyutilized to form a body in accordance with the present invention;

FIG. 4a is a photomicrograph taken at 100× of a body made in accordancewith Example 3;

FIG. 4b is a photomicrograph taken at 400× of a sample made inaccordance with Example 3;

FIG. 5 is a photomicrograph taken at 400× of a sample made in accordancewith Example 4;

FIGS. 6a-6v are photomicrographs and fractographs taken at variousmagnifications (identified in specification) corresponding to samplesmade in accordance with Example 6;

FIG. 7a corresponds with a photomicrograph take at 400× of a sample madein accordance with Example 7;

FIGS. 7b and 7c correspond to fractographs taken at 500× and 1000×,respectively, and correspond to samples made in accordance with Example7;

FIGS. 8a and 8b are photographs of samples made in accordance withExample 8;

FIG. 9 is a schematic cross-sectional view of an assembly utilized tomake samples in accordance with the present invention;

FIGS. 10a-10c are before and after views of samples treated inaccordance with the present invention;

FIGS. 11a-11e correspond to fractographs taken at various magnifications(specified in specification) of samples made in accordance with Example11;

FIG. 12 is a photomicrograph taken at 400× of the microstructure of asample made in accordance with Example 12;

FIG. 13 is a perspective view of a mold piece utilized in accordancewith Example 13;

FIG. 14 is a schematic cross-sectional view of an assembly utilized tomake samples in accordance with Example 17;

FIG. 15 is a schematic cross-sectional view of an assembly utilized tomake samples in accordance with Example 19;

FIG. 16a is a schematic cross-sectional view of an assembly utilized tomake samples in accordance with Example 20;

FIG. 16b is a photomicrograph taken at about 400× of a sample made inaccordance with Example 20;

FIG. 17 is a photomicrograph taken at about 200× of a sample made inaccordance with Example 21;

FIGS. 18a -18c are photomicrographs taken at various magnifications(identified in the specification) corresponding to samples made inaccordance with Example 23; and

FIG. 19 is a photomicrograph taken at about 4000× of the microstructureof sample made in accordance with Example 24.

DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS

In accordance with the present invention, there are provided a pluralityof methods for producing self-supporting bodies. Specifically, at leastone vapor-phase parent metal is caused to react with at least one solidoxidant-containing material to form a solid reaction product.

In all embodiments of the invention, the following processing steps areutilized. A material, at least a portion of which comprises a solidoxidant, is placed into a reaction chamber. The reaction chamber shouldbe made of, or at least coated with, a material which does not adverselyreact with any of the materials utilized in the process of the presentinvention. Moreover, the reaction chamber should be capable of isolatingall materials contained therein from any external contaminants whichmight adversely impact the process of the present invention. Avapor-phase parent metal source is contained within the reaction chamberin a manner which permits an interaction between the parent metal vaporand the solid oxidant-containing material. The parent metal vapor can beintroduced by providing a solid source of parent metal within thereaction chamber, or contiguous to the reaction chamber, and heating thesolid source of parent metal until a temperature is achieved whichresults in an adequate vapor pressure of the parent metal being presentin the reaction chamber. The parent metal vapor should be capable ofcontacting that portion of the solid oxidant-containing material whichis to react with the parent metal vapor. Accordingly, only a portion ofa solid oxidant-containing material may be exposed to the parent metalvapor to create a reaction product or alternatively, substantially allof a solid oxidant-containing material can be exposed to a parent metalvapor to create reaction product.

The solid oxidant-containing material which is to react with the parentmetal vapor should be, or contain, a material which is itself capable ofreacting with the parent metal vapor to form reaction product, or shouldbe capable of being coated with a material which contains a solidoxidant which is capable of forming a desirable reaction product whencontacted with a parent metal vapor.

For example, a category of materials which have been given a substantialamount of attention for many high temperature applications is thegraphite or carbonaceous materials. Specifically, carbon-based materials(e.g., carbon/carbon composites, solid forms of graphite; etc.) haveachieved a substantial amount of attention because they are relativelylight in weight, have excellent high temperature properties, are thermalshock resistant, and have desirable electrical properties. However, theuse of carbon-based materials for many applications has been limited dueto the poor oxidation and/or erosion (e.g., abrasion) resistanceinherent to these materials. Thus, many approaches for forming some typeof protective coating on carbon-based materials have been attempted. Thetechniques of the present invention are well suited for coatingcarbon-based materials and/or substantially completely convertingcarbon-based materials to another material (e.g., a ceramic or ceramiccomposite material) which may be more desirable for a particular purposeor application. The techniques of the invention are also well suited forcoating certain molybdenum-containing materials. This disclosure willfocus primarily upon methods for parent metals reacting withcarbon-based materials, however, it should be understood that thepresent invention can be utilized with materials other than graphite orcarbon-based materials.

In an effort to explain the workings of the present invention, butwithout wishing to be bound by any particular theory or explanation forthe present invention, it appears as though when a parent metal vaporcontacts a solid oxidant, the parent metal vapor first may be adsorbedonto a surface of a solid oxidant-containing material until asubstantially uniform, but very thin, layer is formed and/or somereaction may occur between the parent metal and the solid oxidantcoating material resulting in a thin reaction product layer. The formedlayer eventually substantially completely isolates the solid oxidantfrom any further direct physical contact with the parent metal vapor.Thus, for reaction product to form, additional atoms or ions of parentmetal should be capable of diffusing through the formed layer and/or, atleast one species in the solid oxidant-containing material should becapable of diffusing in an opposite direction toward the parent metalvapor through the same formed layer, to permit additional reaction tooccur. The respective rates of diffusion of parent metal ions and solidoxidant through the formed layer will directly impact the nature andproperties of the composite body which is formed. Stated morespecifically, a directed metal oxidation reaction will occur when therate of diffusion of the solid oxidant through the formed layer isgreater than the rate of diffusion of parent metal ions through theformed layer thus, resulting in a build-up or layer of material on asurface of a solid oxidant-containing material. By controlling variousprocessing parameters such as parent metal composition, parent metalvapor pressure, solid oxidant composition, location of solid oxidantwithin or on another substantially non-reactive material, temperature,processing time, etc., the resulting composite body may compriseanything from a substrate solid oxidant-containing material having atleast one portion of its surface covered with reaction product, to asubstantially completely converted solid oxidant-containing material(e.g., carbon being converted to titanium carbide).

In a first preferred embodiment of the invention, a solidoxidant-containing material is comprised substantially completely ofsolid oxidant which is capable of reacting with parent metal vapor underthe process conditions of the invention. Accordingly, for example, acarbonaceous material is placed within a reaction chamber and is placedinto contact with parent metal vapor (e.g., titanium, hafnium,zirconium, silicon and/or niobium) to result in the formation of aparent metal carbide reaction product. The amount of reaction productthat can form includes: (1) a relatively thin layer of reaction productformed upon a carbonaceous substrate material, (2) a relatively thicklayer of reaction product formed upon a carbonaceous substrate material,or (3) substantially complete conversion of the substrate material toreaction product.

In a second preferred embodiment of the invention, a composite materialcan be formed. Specifically, a solid oxidant substrate is first coatedwith a substantially inert filler material prior to being exposed to aparent metal vapor. A reaction product of parent metal vapor and solidoxidant is then formed and the substantially inert filler material isthereafter embedded in the formed reaction product, thereby forming acomposite material. The filler material may comprise any particularshape or combination of shapes of filler material, and may have anysuitable chemical constituency. However, the filler material should bechosen so as to be capable of surviving the process of the presentinvention. Moreover, by appropriate selection of filler material(s) tobe embedded by reaction product, a wide range of desirable propertiescan be achieved.

In a third preferred embodiment of the invention, a solidoxidant-containing substrate material is first coated or contacted withat least one material which will react with at least one other materialexternal to the solid oxidant (e.g., in the coating), and/or react withat least one material in the solid oxidant-containing material, and/orreact with the parent metal vapor. For example, a powdered parent metalhaving a substantially similar or substantially different compositionfrom the parent metal vapor, may be first placed as a coating onto atleast a portion of a surface of a solid oxidant-containing materialprior to the parent metal vapor contacting the solid oxidant-containingmaterial. Reactions may then occur between the powdered parent metal onthe surface of the solid oxidant-containing material and the solidoxidant itself and/or reactions may occur between the powdered parentmetal on the solid oxidant-containing material and the parent metalvapor. Additionally, at least one solid oxidant (e.g., boron carbide)which is different in composition from the solid oxidant-containingsubstrate material (e.g., carbon) may be placed onto the surface of thesolid oxidant-containing material prior to contacting the parent metalvapor with the solid oxidant-containing material. The different solidoxidant placed on the surface of a solid oxidant-containing materialsubstrate should be capable of reacting with the parent metal vapor toresult in a reaction product which may be different from the reactionproduct which results when the parent metal vapor reacts with thesubstrate solid oxidant-containing material. This different reactionproduct could serve as a filler material. Still further, a powderedparent metal (e.g., titanium, hafnium, zirconium, silicon and/orniobium) having a substantially similar or substantially differentchemical composition from the parent metal vapor (e.g., titanium,hafnium, zirconium, silicon and/or niobium) may be mixed with a solidoxidant powder which is different in composition from the solidoxidant-containing material substrate to permit the formation of areaction product which is different than the reaction product whichforms when the parent metal vapor contacts the substrate solidoxidant-containing material. This different reaction product could alsoserve as a filler material. Further, if more than one reaction productis formed, it is possible that the reaction products may also react witheach other.

In a fourth preferred embodiment of the invention, each of the first andthird embodiments discussed above can be expanded on by positioning afiller material on at least a portion of the surface of the solidoxidant-containing material. Accordingly, the filler material could beuniformly or non-homogeneously mixed with, for example, a powderedparent metal of substantially similar or substantially differentcomposition than the vapor-phase parent metal. Moreover, the fillermaterial could be mixed in a substantially uniform or non-homogeneousmanner with a solid oxidant powder which is placed onto the surface of asolid oxidant-containing substrate material. Still further, a fillermaterial may be mixed either substantially uniformly ornon-homogeneously with the combination of a parent metal powder (havinga substantially similar or substantially different composition than aparent metal vapor) and a solid oxidant.

In a fifth preferred embodiment of the invention, a solidoxidant-containing material is placed as a coating on a substratematerial which normally would not react with a parent metal vapor so asto permit the formation of a reaction product coating having acomposition different than the solid oxidant-containing material coatingand the substrate material.

Further, in each of the above-discussed embodiments, it is possible tosupply substantially simultaneously more than one parent metal vapor topermit the formation of an even greater number of reaction products andpossible interactions between forming or formed reaction products.

It should be understood that a large number of combinations of parentmetal vapors, solid oxidant-containing materials, solid oxidant powders,parent metal powders, etc., are possible for utilization in accordancewith the teachings of the present invention. Thus, while every potentialcombination of materials has not been expressly discussed above herein,such combinations should readily occur to those skilled in the art.

EXAMPLE 1

The following Example demonstrates a method for forming a reactionproduct coating on a graphite substrate by reacting a parent metal vaporwith the graphite substrate at an elevated temperature.

FIG. 1 is a cross-sectional schematic of the lay-up used to form areaction product coating on a graphite substrate coupon. Specifically,FIG. 1 is a cross-sectional schematic of a vapor deposition chambercontained in a containment graphite boat 43. The vapor depositionchamber was comprised of a lower chamber portion 31, three substratesupporting rods 35 attached to sidewalls of the lower chamber portion31, four parent metal source trays 34 and 33, made of graphite, withinlower chamber portion 31, an upper chamber portion 32, a stack portiontube 36 containing a perforated plate 37 and attached to upper chamberportion 32, a closed end tube 41 covering the stack portion tube 36 andgraphite felt getters 40 and 42 wrapped around stack portion tube 36 andvapor deposition chamber respectively.

More specifically, the lower chamber portion 31 of the vapor depositionchamber measured about 6.5 inches (165 mm) long, about 6.5 inches (165mm) wide, about 4 inches (102 mm) high and had a wall thickness of about0.25 inches (6.4 mm). The lower chamber portion 31 was machined from apiece of Grade ATJ graphite (Union Carbide Corporation, Carbon ProductsDivision, Cleveland, Ohio). The three graphite support rods 35 withdiameters of about 0.38 inch (9.6 mm) and made from Grade AGSX graphite(Union Carbide Corporation, Carbon Product Division, Cleveland, Ohio),were interference fit into holes in the sidewalls of the lower chamberportion 31. All of the support rods 35 were located about 2.0 inches (51mm) from the bottom of the lower chamber portion 31. Additionally, eachof the three support rods 35 were located about 1.0 inch (25 mm), about1.75 inches (45 mm), and about 4.13 inches (105 mm), respectively, fromone sidewall of the lower chamber portion 31 and extended from onesidewall to the opposite sidewall of the lower chamber portion 31. Thesupport rods 35 formed a supporting means for holding the graphitesubstrate coupons during coating.

The upper chamber portion 32 of the vapor deposition chamber measuredabout 6.5 inches (165 mm) long, about 6.5 inches (165 mm) wide, about 4inches (102 mm) high, and had a wall thickness of about 0.25 inches (6.4mm). The upper chamber portion 32 further included a hole 44 having adiameter of about 1.75 inches (44.5 mm). The hole 44 was substantiallycentrally located in a top portion of the upper chamber portion 32. Thestack portion tube 36 measured about 5.5 inches (140 mm) long, had anouter diameter of about 2.25 inches (57 mm), and had a wall thickness ofabout 0.25 inches (6.4 mm). The stack portion tube 36 was also machinedfrom Grade ATJ graphite. The open end of stack portion tube 36 wasaligned with the hole 44 within the top of upper chamber portion 32 andglued to the upper chamber portion 32 with RIGIDLOCK® graphite cement(Polycarbon Corporation, Valencia, Calif.). Additionally, about 10 slots38 were cut in the closed end of stack portion tube 36. Each slot 38measured about 0.04 inch (1 mm) wide and about 0.5 inch (13 mm) deep andprovided a means for communicating between inner cavity of the vapordeposition chamber and the atmosphere external to vapor depositionchamber. The perforated plate 37 measured about 0.25 inch (6.4 mm)thick, had an outer diameter of about 1.75 inches (44.5 mm) and hadthree equally spaced holes for communicating with the atmosphereexternal to the vapor deposition chamber. Each hole 45 throughperforated plate 37 had an about 0.4 inch (10 mm) diameter. Theperforated plate 37 was secured with RIGIDLOCK® graphite cement withinstack portion tube 36 about 1.38 inches (35 mm) from the inner surfaceof upper chamber portion 32. The Grade GH graphite felt 40 (FiberMaterials, Inc. Biddeford, Me.) had a thickness of about 0.125 inch (3.2mm) and was wrapped around the outer diameter and along the length ofstack portion tube 36.

The closed end tube 41 measured about 4 inches (102 mm) long, had anouter diameter of about 3 inches (76 mm), and had a wall thickness ofabout 0.25 inch (6.4 mm). The closed end tube 41 was placed over stackportion tube 36 to secure graphite felt 40.

The parent metal source trays were machined from Grade ATJ graphite. Oneparent metal source tray 34 measured about 3.5 inches (89 mm) long,about 3.5 inches (89 mm) wide, about 1 inch (25 mm) high and had a wallthickness of about 0.25 inch (6.4 mm). The parent metal source tray 34was placed in one corner of lower chamber portion 31. The threeadditional parent metal source trays 33 (only one shown in FIG. 1)measured about 2.5 inches (64 mm) long, 2.5 inches (64 mm) wide, 1 inch(25 mm) high and had a wall thickness of about 0.25 inch (6.4 mm). Thethree additional parent metal source trays 33 were placed in theremaining space of the bottom of lower chamber portion 31. All theparent metal source trays 34 and 33 were filled with titanium metalsponge material 46 to a depth ranging from about 0.25 inch (6.4 mm) toabout 0.38 inch (9.7 mm) and therefore a total weight of about 100grams.

The edges of a graphite substrate coupon of Grade AXZ-5Q graphitematerial (Poco Graphite, Inc., Decatur, Tex.), measuring about 1 inch(25 mm) long, about 1 inch (25 mm) wide and about 0.2 inch (5.1 mm)thick, were smoothed by sanding with 400 grit (average particle size ofabout 23 μm) silicon carbide paper. All the surfaces of the graphitesubstrate coupon were roughened by sanding with 1200 grit (averageparticle size of about 4 μm) silicon carbide paper. The sanded graphitesubstrate coupon 47 was then cleaned for about 15 minutes in anultrasonically agitated bath of acetone and dried in an air oven set atabout 120° C. for about 0.5 hour. After drying substantially completely,the graphite substrate coupon 47 was placed on support rods 35 withinlower chamber portion 31 and upper chamber portion 32 was placed incontact with lower chamber portion 31 to form the vapor depositionchamber. The Grade GH graphite felt 42 measured about 8 inches (203 μm)wide and had an about 0.125 inch (3.2 mm) thickness. The graphite felt42 was wrapped around the outer perimeter of the vapor depositionchamber twice. Graphite clamps 48 were used to secure the graphite felt42 to the vapor deposition chamber 30, thus completing the formation ofthe setup. The setup was then placed into a larger containment graphiteboat 43 to form a lay-up.

The lay-up and its contents were then placed into a vacuum furnace andthe vacuum furnace door was closed. The vacuum furnace was thenevacuated to a pressure of about 0.2 millitorr. After about 50 minutesat about 0.2 millitorr, the vacuum furnace and its contents were heatedto about 500° C. at about 250° C. per hour while maintaining a pressureless than about 60 millitorr. The vacuum furnace was then heated fromabout 500° C. to about 1000° C. at about 500° C. per hour whilemaintaining a pressure less than about 60 millitorr. At about 1000° C.,the pressure within the vacuum furnace was allowed to increase tobetween about 60 millitorr to about 250 millitorr and the vacuum furnaceand its contents were heated from about 1000° C. to about 1900° C. atabout 500° C. per hour. After about 2 hours at about 1900° C. with apressure ranging from about 60 millitorr to about 250 millitorr, thevacuum furnace and its contents were cooled at about 350° C. per hour toabout room temperature while maintaining a pressure ranging from about60 millitorr to about 250 millitorr. At about room temperature, thevacuum pump was turned off, the vacuum furnace was allowed to adjust toatmospheric pressure and the lay-up and its contents were removed fromthe furnace.

After the setup was disassembled, the graphite substrate coupon wasremoved from the lower chamber portion 31 of the vapor depositionchamber 30 and it was noted that a mirror like finish coated the surfaceof the graphite substrate coupon. Results of x-ray diffraction analysisof the ceramic composite coating indicated that constituents of theceramic composite coating included, among other phases, TiC and C. Thegraphite substrate coupon was then cut, mounted and polished formetallographic examination as well as examination in a scanning electronmicroscope. Specifically, FIG. 2a is a microstructure taken at about400× of the ceramic composite coating 51 on the graphite substratecoupon 52 and FIG. 2b is a fractograph taken at about 200× in a scanningelectron microscope of the composite coating 51 on the graphitesubstrate coupon 52.

EXAMPLE 2

This Example further demonstrates a method for forming a reactionproduct coating on a graphite substrate by reacting a parent metal vaporwith a graphite substrate at an elevated temperature.

FIG. 3 is a cross-sectional schematic of the lay-up used to form areaction product coating on a graphite substrate coupon. Specifically,FIG. 3 is a cross-sectional schematic of a vapor deposition chamber 72in a containment graphite boat 71. The vapor deposition chamber 72 wascomprised of a graphite plate 60, ten stackable source trays 61, asubstrate support chamber portion 62, five substrate supporting rods 63attached to side walls of stackable support chamber portion 62, agraphite lid 64 having holes therein, a graphite felt 68 substantiallycovering the holes in graphite lid 64, four stackable module alignmentrods 65 attached to graphite plate 60 by threaded graphite rod 66 andfastened with nut 67, stackable module alignment clamps 69 engagingstackable module alignment rods 65 via set screw 70.

More specifically, graphite plate 60 was made from Grade ATJ graphite(Union Carbide Corporation, Carbon Products Division, Cleveland, Ohio).Additionally, graphite plate 60 measured about 6.5 inches (165 mm) long,6.5 inches (165 mm) wide, and 0.5 inches (13 mm) thick. The mid pointsof the face of graphite plate 60 that measured about 6.5 inches (165 mm)long and about 0.5 inches (13 mm) high were drilled and tapped to acceptthe threaded graphite rod 66.

Stackable parent metal source trays 61 measured about 6.5 inches (165mm) long, about 6.5 inches (165 mm) wide, 0.75 inches (19 mm) high andhad a wall thickness of about 0.25 inches (6.4 mm). A hole substantiallyin the center of the 6.5 inch (165 mm) long and 6.5 inch (165 mm) wideportion of stackable parent metal source tray 61 measured about 2 inches(51 mm) long and about 2 inches (51 mm) wide. Along the perimeter the 2inches (51 mm) long and 2 inches (51 mm) wide hole was fastened withRIGIDLOCK® graphite cement (Polycarbon Corporation, Valencia, Calif.), a2.5 inches (64 mm) long, 2.5 inches (64 mm) wide, 0.25 inch (6.4 mm)high and 0.25 inch (6.4 mm) thick graphite rectangular frame in order tocomplete the formation of the stackable metal source trays 61.

Stackable substrate support chamber portion 62 measured about 6.5 inches(165 mm) long, 6.5 inches (165 mm) wide, 2.0 inches (51 mm) high, andhad a wall thickness of about 0.25 inches (6.4 mm). Five substratesupport rods 63, each having a diameter of about 0.38 inches (9.6 mm)and measuring about 6.5 inches (165 mm) long, were interference fit intothe side walls of substrate support chamber portion 62. All of thesupport rods 63 were located about 1.0 inches (25 mm) from the bottom ofthe substrate support chamber portion 62. Additionally, each of the fivesupport rods 63 were located about 1 inch (25 mm), about 2 inches (51mm), about 3 inches (76 mm), about 4 inches (102 mm), and about 5 inches(127 mm), respectively from one side wall from the substrate supportchamber portion 62 and extended from one side wall to the opposite sidewall of the substrate support chamber portion 62. The support rods 63formed a supporting means for holding the graphite substrate couponsduring coating.

The graphite lid 64 measured about 6.5 inches (165 mm) long, about 6.5inches (165 mm) wide, and about 0.25 inch (6.4 mm) thick. About 5 holeswere substantially centrally located in graphite lid 64 and provided ameans for communicating with the atmosphere external to vapor depositionchamber 72. Each hole measured about 0.25 inches in diameter.

Vapor deposition chamber 72 was assembled by first placing graphiteplate 60 on a leveled table top. A designated number of stackable parentmetal source trays 61, made of graphite, were then filled with about 250grams of a zirconium sponge material (Western Zirconium, Ogden, Utah)having a diameter ranging from about 0.033 inch (0.84 mm) to about 0.25inch (6.4 mm). The zirconium sponge material was evenly distributedwithin each stackable parent metal source tray. Five stackable parentmetal source trays 61 were placed one on the other, on the graphiteplate 60 and were substantially aligned. A substrate support chamberportion 62 was then placed onto and aligned with the give stackableparent metal source trays 61. A graphite substrate coupon 73,substantially the same as and prepared in substantially the same manneras the graphite substrate coupon described in Example 1, was placedwithin the substrate support chamber portion 62 on substrate supportrods 63. The five additional stackable parent metal source trays 61,each having about 250 grams of a zirconium sponge material therein, werestacked above the substrate support chamber portion 62. The graphite lid64 was then placed on top of the upper most stackable parent metalsource tray 61. Four stackable module alignment bars 65, measuring about10.25 inches (260 mm) long, 2.0 inches (51 mm) wide, and about 0.38 inch(9.6 mm) thick and having a hole at one end for receiving threadedgraphite rod 66 were placed over and secured to threaded graphite rod 66to substantially align the ten stackable parent metal source tray 61 andthe substrate support chamber portion 62 and the graphite lid 64. Atleast three layers of Grade GH graphite felt 68 (Fiber Materials, Inc.,Biddeford, Mass.) measuring about 0.125 inches (3.2 mm) thick wereplaced over the holes in graphite lid 64. A first module alignment clamp69 measuring about 8 inches (203 mm) long, 1 inch (25 mm) wide and about0.25 inch (6.4 mm) thick with extending end portions measuring about 1inch (25 mm) long, 1 inch wide (25 mm) and about 0.5 inch (1.3 mm)thick, was placed in contact with graphite felt 68 such that extendingend portion containing set screw 70 aligned with stackable modulealignment bar 65. Set screw 70 in module alignment clamp 69 was thenadjusted to secure stackable module alignment bar 65 against graphitelid 64, stackable parent metal source trays 61 and substrate supportchamber portions 62. A second module alignment clamp 69 was placed incontact with and perpendicular to the first module alignment clamp 69and the sets screws 70 were tighten to a second set of stackable modulealignment bars 65 aligning graphite lid 64, substrate support chamber62, and stackable parent metal source trays 61 and completing theformation of the set-up. The set-up comprising the vapor depositionchamber was then placed into a containment graphite boat 71 to form alay-up.

The lay-up and its contents were placed in a vacuum furnace and thevacuum furnace door was closed. The vacuum furnace was evacuated inabout 15 minutes and then filled with argon. After the vacuum furnacewas substantially completely filled with argon, the vacuum furnace wasevacuated to a pressure of about 0.12 millitorr. The vacuum furnace andits contents were then heated to about 1000° C. at about 350° C. perhour while maintaining a pressure less than about 60 millitorr. Thefurnace was then heated from about 1000° C. to about 2000° C. at about350° C. per hour while maintaining a pressure between about 60 millitorrand about 250 millitorr. After about 5 hours at about 2000° C. with apressure ranging from about 60 millitorr to about 250 millitorr, thevacuum furnace and its contents were cooled at about 350° C. per hour toabout room temperature. At about room temperature, the vacuum pump wasturned off, the vacuum furnace was allowed to come to atmosphericpressure, and the lay-up and its contents were removed from the vacuumfurnace.

After the setup was disassembled, the graphite substrate coupon wasremoved from within the substrate support chamber portion 62 of thevapor deposition chamber 72 and it was noted that a metallic like finishcoated the graphite substrate coupon. The graphite substrate coupon wascut, mounted and polished for metallographic examination. Specifically,the examination of the ceramic composite coating using opticalmicroscopy revealed that a ceramic composite coating thickness of about73 μm had been formed on the graphite substrate coupon. Analysis of theceramic composite coating by x-ray diffraction indicated thatconstituents of the ceramic composite coating included, among otherphase, ZrC and C.

EXAMPLE 3

The following Example demonstrates a method for forming a reactionproduct coating comprising a ceramic matrix composite coating on agraphite substrate by applying to the surface of a graphite substrate amixture comprising a parent metal powder and a boron carbide powder andheating the powder covered graphite substrate in the presence of aparent metal vapor to permit a reaction between the parent metal powder,the boron carbide, the parent metal vapor and/or the graphite substrate.

The method of Example 1 was substantially repeated except that a smallervapor deposition chamber was used. Specifically, the outer dimensions ofthe smaller vapor deposition chamber measured about 3.5 inches (89 mm)long, 3.5 inches (89 mm) wide and about 7 inches (178 mm) high and thestack portion measured about 3.25 inches (83 mm) long, had an about 1.25inches (32 mm) diameter and had a wall thickness of about 0.25 inch (6.4mm). Only one graphite parent metal source tray measuring about 2.5inches (64 mm) long, 2.5 inches (64 mm) wide, 1 inch (25 mm) high andhaving a wall thickness of about 0.25 inch (6.4 mm), was placed in thebottom of the lower chamber portion of the smaller vapor depositionchamber.

A substrate coupon of Grade AXZ-5Q graphite (Poco Graphite, Inc.,Decatur, Tex.), measuring about 1 inch (25 mm) long, about 1 inch (25mm) wide and about 0.2 inch (5.1 mm) thick, was prepared for coating byhand sanding the edges of the substrate with 400 grit (average particlesize of about 23 μm) silicon carbide abrasive paper until the edges weresubstantially smooth. All the surfaces of the graphite substrate couponwere toughened by sanding with 1200 grit (average particle diameter ofabout 4 μm) silicon carbide paper. The sanded graphite substrate couponwas then cleaned for about 15 minutes in an ultrasonically agitated bothof acetone and dried in an air oven set at about 120° C. for about 0.5hour. A slurry mixture comprised of by weight about 66.3% -325 mesh(particle size less than about 45 μm) zirconium powder (ConsolidatedAstronautics, Saddle Brook, N.J.), about 9.5% TETRABOB® M-16 1000 grit(average particle size of about 5 μm) boron carbide (ESK-EngineeredCeramics, New Canaan, Conn.), about 24.0% deionized water and about 0.2%XUS-40303.00 tertiary amide polymer ceramic binder (Dow ChemicalCompany, Midland, Mich.) was prepared by combining the slurry mixturecomponents in a plastic jar and roll mixing on a jar mill for at least 2hours. A portion of the slurry mixture was applied onto one of thetoughened surfaces of the graphite substrate coupon. Three separatecoats of the slurry mixture were applied onto the toughened surface.Each application of the slurry mixture was allowed to air dry before thenext application was made. After the three slurry mixture applicationshad substantially completely air dried to form a powder coating, thepowder coated graphite substrate coupon was placed in a forced air ovenset at about 45° C. After about 0.5 hour at about 45° C., the powdercoated graphite substrate coupon was moved to a second forced air ovenset at about 120° C. for about an additional 0.5 hour. After drying, thepowder coating thickness on the graphite substrate coupon measured about0.07 inch (432 μm) and weighed about 0.39 grams. As in Example 1, thesetup was placed into a larger containment graphite boat to form thelay-up.

The lay-up and-its contents were placed into a vacuum furnace and thefurnace door was closed. The vacuum furnace was evacuated in about 15minutes and then filled with argon. After the vacuum furnace wassubstantially completely filled with argon, the vacuum furnace wasevacuated to a pressure of about 0.12 millitorr. The vacuum furnace andits contents were then heated to about 1000° C. at about 350° C. perhour while maintaining a pressure less than about 60 millitorr. Thevacuum furnace was then heated from about 1000° C. to about 2000° C. atabout 350° C. per hour while maintaining a pressure ranging from about60 millitorr to about 250 millitorr. After about 5 hours at about 2000°C. with a pressure ranging from about 60 millitorr to about 250millitorr, the vacuum furnace and its contents were cooled at about 350°C. per hour to about room temperature. At about room temperature, thevacuum pump was turned off, the vacuum furnace was allowed to come toabout atmospheric pressure, and the lay-up and its contents were removedfrom the vacuum furnace.

After the setup was disassembled, the graphite substrate coupon wasremoved from the lower chamber portion of the smaller vapor depositionchamber and it was noted that a metallic like finished coated thesurface of the graphite substrate. The graphite substrate was then cut,mounted and polished for metallographic examination. Specifically, FIG.4a is a microstructure taken at about 100× of the ceramic compositecoating 51 on the graphite substrate 52. FIG. 4b is a microstructuretaken at about 400× of the ceramic composite coating illustrating theplatelet morphology of the ceramic composite coating 51.

EXAMPLE 4

The following Example demonstrates a method for forming a reactionproduct coating on a graphite substrate by applying to the surface ofthe graphite substrate a mixture comprising a boron powder and heatingthe powder covered graphite substrate in the presence of a parent metalvapor to permit the reaction between the boron powder, the parent metalvapor and/or the graphite substrate.

The method of Example 1 was substantially repeated except for themethods of preparing and coating the surface of the graphite substratecoupon. Specifically, the surface of the Grade AXZ-5Q graphite substratecoupon was abraded with 1200 grit (average particle size of about 4 μm)silicon carbide paper to smooth all the surfaces. The sanded graphitesubstrate coupon was-then cleaned for about 15 minutes in anultrasonically agitated bath of acetone and dried in a forced air ovenset at about 120° C. for about 0.5 hours. After drying substantiallycompletely, the graphite substrate coupon was coated with a solutioncomprised of by weight about 10 percent GAF® PVP K-15 polyvinylpyrrolidone (GAF Chemical Corporation, Wayne, N.J.) and ethanol. Afterallowing the coating on the surface of the graphite substrate coupon toair dry for about 15 minutes, the graphite substrate coupon was placedin a forced air oven set at about 120° C. After about 0.5 hour at about120° C., the graphite substrate coupon was removed from the forced airoven and cooled to about room temperature. At about room temperature,one side of the graphite substrate coupon was coated with a slurrycomprised of by weight between about 20 to 30 percent submicron boronpowder (Callery Chemical Co., Callery, Pa.) and the balance ethanol.Excess slurry was wiped off the side of the graphite substrate couponand the graphite substrate coupon was substantially dried. At about roomtemperature, the graphite substrate coupon was again coated with asolution comprised of by weight of about 75 to about 85 percent ELMER'S®professional carpenter's wood glue and the balance deionized water. Thegraphite substrate coupon was then swabbed with an additional amount ofdeionized water. While the wood glue deionized water solution was stillwet, -325 mesh (particle diameter less than about 45 μm) boron powder(Consolidated Astronautics, Inc. Saddle Brook, N.J.) was hand siftedonto one surface of the graphite substrate coupon. Excess boron powder,that had not adhered to the surface of the graphite substrate coupon,was brushed off with a camel's hair brush. The powder coated graphitesubstrate coupon was then placed in a forced air oven set at about 45°C. After about 0.5 hour at about 45° C., the powder coated graphitesubstrate coupon was moved to a second forced air oven set at about 120°C. After about 0.5 hour at about 120° C. in the second forced air oven,the powder coated graphite substrate coupon was removed and allowed tocool to about room temperature. Once at about room temperature, thepowder coated graphite substrate coupon was placed onto the substratesupport rods 35 (refer to FIG. 1) within the lower chamber portion 30 ofthe vapor deposition chamber 32 and the upper chamber portion 32 wasplaced over the lower chamber portion.

Additional exceptions of this Example relative to Example 1 were thatthe titanium sponge material (Oregon Metallurgical Corporation, Albany,Ore.) weighing about 400 grams, was not placed into a graphite metalsource trays but directly into the bottom of the lower chamber portion31 of the vapor deposition chamber 30 and the stack portion 36 of thevapor deposition chamber was not covered with dosed end crucible 41. Thevapor deposition chamber 30 was placed into a containment graphite boat43 to complete the formation of the lay-up.

The lay-up and its contents were placed into a vacuum furnace and thevacuum furnace door was closed. The vacuum furnace was then evacuated.After about 0.5 hour under a pressure less than about 60 millitorr, thevacuum furnace was heated to about 500° C. at about 250° C. per hour andthen from about 500° C. to about 1000° C. at about 500° C. whilemaintaining a pressure less than 60 millitorr. At about a 1000° C., thepressure was allowed to increase to between about 60 millitorr and about250 millitorr and the vacuum furnace was heated to about 1900° C. atabout 500° C. per hour. After about 2.5 hours at about 1900° C., whilemaintaining a pressure between about 60 millitorr and about 250millitorr, the vacuum furnace and its contents were cooled to about roomtemperature at about 350° C. per hour. At about room temperature, thevacuum pump was turned off, the vacuum furnace was allowed to come toabout atmospheric pressure, and the lay-up and its contents were removedfrom the vacuum furnace.

After the lay-up was disassembled, the graphite substrate coupon wasremoved from within the lower chamber portion of the vapor depositionchamber and it was noted that a metallic appearing finish coated thegraphite substrate coupon. The graphite substrate coupon was then cut,mounted and polished for metallographic examination. Specifically, theexamination of the ceramic coating by optical microscopy revealed that acoating thickness of about 200 μm had been formed. Results of x-raydiffraction analysis indicated that ceramic composite coating comprisedamong other phases, TiB₂ and TiC. Specifically, FIG. 5 is amicrostructure taken at about 400× of the ceramic composite coating 51on the graphite substrate coupon 52.

EXAMPLE 5

The following Example demonstrates a method for forming a reactionproduct coating on a graphite substrate by applying to the surface of agraphite substrate a boron carbide powder and heating the powder coveredsubstrate in the presence of a parent metal vapor to permit the reactionbetween the boron carbide power, the parent metal vapor and/or thegraphite substrate.

The method of Example 1 was substantially repeated except for themethods of preparing and coating the surface of the graphite substratecoupon. Specifically, a solution comprised by weight of about 6 percentELVACITE® 2045 acrylic resin (E.I. du Pont de Nemours and Company, Inc.,Wilmington, Del.), 0.06 percent n-butyl phthalate (Fisher ScientificCompany, Pittsburgh, Pa.), about 42.28 percent isopropyl alcohol, andabout 51.66 percent ethylene glycol monobutyl ether (Textile ChemicalCompany, Reading, Pa.), was combined in a plastic jar and placed on ashaker to effect mixing. After about 0.5 hour on a shaker, the plasticjar was removed to a slow roll jar mill. After about 1 hour on the slowroll jar mill, an amount of TETRABOR® 1000 grit (average particlediameter 5 μm) boron carbide powder (ESK Engineered Ceramics, NewCanaan, Conn.) was added to the solution to make a slurry mixturecomprising by weight about 50% boron carbide and about 50% solution. Theplastic jar was replaced to the slow roll jar mill to suspend the boroncarbide in the solution and thereby form a slurry mixture. After atleast about an 0.5 hour on the slow roll jar mill, a slurry mixture wasformed and applied to the surface of the graphite substrate coupon thathad been prepared as described in Example 4. After the slurry mixture onthe graphite substrate coupon had substantially dried, the powdercovered graphite substrate coupon was placed into the graphite supportrods in the lower portion of the vapor deposition chamber. The vapordeposition chamber was then placed into a containment graphite boat tocomplete the formation of the lay-up.

The lay-up and its contents were placed in a vacuum furnace and thevacuum furnace door was closed. The vacuum furnace was evacuated to apressure of about 0.12 millitorr. After about 25 minutes at about 0.12millitorr, the vacuum furnace and its contents were heated from aboutroom temperature to about 500° C. at about 250° C. per hour and thenfrom about 500° C. to about 1000° C. at about 500° C. per hour whilemaintaining a pressure less than about 60 millitorr. The vacuum furnacewas then heated from about 1000° C. to about 1900° C. at about 500° C.per hour while maintaining a pressure between about 60 millitorr andabout 250 millitorr. After about 2 hours at about 1900° C. with apressure ranging between about 60 millitorr and about 250 millitorr, thevacuum furnace and its contents were cooled at about 350° C. per hour toabout room temperature. At about room temperature, the vacuum pump wasturned off and the vacuum furnace pressure was allowed to increase toabout atmospheric pressure. At about room temperature and the lay-up andits contents were removed from the vacuum furnace. The setup wasdisassembled and the graphite substrate coupon was removed from withinthe lower chamber portion of the vapor deposition chamber. It was notedthat a metallic appearing finish coated the surface of the graphitesubstrate coupon. Results of x-ray diffraction analysis indicated thatthe ceramic composite coating comprised, among other phases, TiC, TiB₂,and B₄ C.

EXAMPLE 6

The following Example demonstrates a method for forming a reactionproduct coating on a graphite substrate by applying to the surface of agraphite substrate an additional powder and heating the powder coveredgraphite substrate in the presence of a parent metal vapor to permit theincorporation of the additive powder in a ceramic composite coatingformed by the reaction between the parent metal vapor and the graphitesubstrate. Table I contains a summary for Sample A through Sample O ofthe additive powder size and composition, the thickness of the additivepowder coating, the processing temperature to effect the formation ofthe ceramic composite coating, the processing time to effect to theformation of the ceramic composite coating and the thickness of theceramic composite coating on a graphite substrate.

Specifically, the composition of the additive powders placed ontographite substrate coupons included: about -325 mesh (particle diameterless than about 45 μm) titanium carbide (Atlantic Equipment Engineers,Bergenfield, N.J.); about 1-5 μm particle diameter titanium diboride(Atlantic Equipment Engineers, Bergenfield, N.J.); about 14.4 μm averageparticle diameter silicon tetraboride (Atlantic Equipment Engineers,Bergenfield, N.J.); about -325 mesh (particle diameter less than about45 μm) silicon hexaboride (Consolidated Astronautics, Inc., SaddleBrook, N.J.), about 12.6 μm average particle diameter hafnium diboride(Vat Lac Oid Chemical Co., Inc., Bergenfield, N.J.); about -325 mesh(particle diameter less than about 45 μm) tungsten monoboride (Cerac,Inc., Milwaukee, Wisc.); about -325 mesh (particle diameter less thanabout 45 μm) di-tungsten pentaboride (Cerac, Inc., Milwaukee, Wisc.);about -325 mesh (particle diameter less than about 45 μm) tantalumdiboride (Atlantic Equipment Engineers, Bergenfield, N.J.); about 1-5 μmparticle diameter titanium nitride (Atlantic Equipment Engineers,Bergenfield, N.J.), about 1-5 μm particle diameter zirconium nitride(Atlantic Equipment Engineers, Bergenfield, N.J.), about -325 mesh(particle diameter less than about 45 μm) pentatitanium trisilicide(Atlantic Equipment Engineers, Bergenfield, N.J.), about 1-5 μm meshparticle diameter titanium disilicide (Atlantic Equipment Engineers,Bergenfield, N.J.), about 1-5 μm molybdenum disilicide (AtlanticEquipment Engineers, Bergenfield, N.J.), about -100 mesh (particlediameter less than about 150 μm) molybdenum (Consolidated AstronauticsCo., Inc., Saddle Brook, N.J.) and about -325 mesh (particle diameterless than about 45 μm) rhenium (Rembar Co., Dobbs, N.Y.). The method ofExample 1 was substantially repeated to prepare the graphite substratecoupon for coating and the method of Example 5 was substantiallyrepeated for Sample A through Sample O in order to slurry coat andeffect the formation of the ceramic composite coating on the graphitesubstrate coupons.

As was done in Example 5, the ceramic composite coated graphitesubstrate coupons were cut, mounted and polished for metallographicexamination and fracture surfaces of the ceramic composite coating onthe graphite substrate coupon were examined using an electronmicroscope. Additionally, analysis of the ceramic composite coating byx-ray diffraction was performed. Specifically, FIG. 6a is a fractographtaken at about 500× the ceramic composite coating 51 on the graphitesubstrate coupon 52 corresponding to Sample A. Results of x-raydiffraction analysis indicated that the constituents of the ceramiccomposite coating on Sample A included, among other phases, TiC.

FIG. 6b is a fractograph taken at about 200× of the ceramic compositecoating 51 on the graphite substrate coupon 52 and FIG. 6c is aphotomicrograph taken at about 400× of the ceramic composite coating 51on the graphite substrate 52 corresponding to Sample B.

FIG. 6d is a fractograph taken at about 200× of the ceramic compositecoating 51 on the graphite substrate coupon 52 and FIG. 6e is aphotomicrograph taken at about 400× of the ceramic composite coating 51on the ceramic substrate coupon 52 and corresponding to Sample C.Results of x-ray diffraction analysis indicated that the constituents inthe area comprising the ceramic composite coating on Sample C includedamong other phases TiC, SiB₄ and C.

FIG. 6f is a fractograph taken at about 500× of the ceramic compositecoating 51 on the graphite substrate coupon 52 and FIG. 6g is aphotomicrograph taken at about 400× of the ceramic composite coating 51ion the graphite substrate 52 corresponding to Sample D. Results ofx-ray diffraction analysis indicated that the constituents in the areacomprising the ceramic composite coating on Sample D included, amongother phases, TiC, TiB₂ and C.

FIG. 6h is a fractograph taken at about 200× of the ceramic compositecoating 51 on the graphite substrate 52 and FIG. 6i is a photomicrographtaken at about 400× of the ceramic composite coating 51 on the graphitesubstrate 52 and corresponding to Sample E. Results of x-ray diffractionanalysis indicated that the constituents in the area comprising theceramic composite coating on Sample E included, among other phases, TiC,C, and HfB₂.

FIG. 6j is a fractograph taken at about 500× of the ceramic compositecoating 51 on the graphite substrate coupon 52 and FIG. 6k is aphotomicrograph taken at about 400× of the ceramic composite coating 51on the graphite substrate coupon corresponding to Sample F. Results ofx-ray diffraction analysis indicated that the constituents in the areacomprising the ceramic composite coating on Sample F included, amongother phases, titanium carbide and carbon.

FIG. 6l is a fractograph taken at about 500× of the ceramic compositecoating 51 on the graphite substrate coupon 52 and FIG. 6m is aphotomicrograph taken at about 400× of the ceramic composite coating 51on the graphite substrate coupon 52 corresponding to Sample G. Resultsof x-ray diffraction analysis indicated that the constituents in thearea comprising the ceramic composite coating on Sample G included,among other phases, TiC and C.

FIG. 6n is a fractograph taken at about 500× of the ceramic compositecoating 51 on the graphite substrate 52 and FIG. 6o is a photomicrographtaken at about 400× of the ceramic composite coating 51 on the graphitesubstrate coupon 52 corresponding to Sample H.

FIG. 6p is a fractograph taken at about 200× of the ceramic compositecoating 51 on the graphite substrate coupon 52 corresponding to SampleI. Results of x-ray diffraction analysis indicated that the constituentsin the area comprising the ceramic composite coating on Sample Iincluded, among other phases, TiC.

FIG. 6q is a fractograph taken at about 500× of the ceramic compositecoating 51 on the graphite substrate 52 and FIG. 6r is a photomicrographtaken at about 400× of the ceramic composite coating 51 on the graphitesubstrate coupon 52 corresponding to Sample J. Results of x-raydiffraction analysis indicated that the constituents in the areacomprising the ceramic composite coating on Sample J included, amongother phases, TiC and C.

FIG. 6s is a fractograph taken at about 200× of the ceramic compositecoating 51 on the graphite substrate coupon 52 corresponding to SampleK. Results of x-ray diffraction analysis indicated that the constituentsin the area comprising the ceramic composite coating on Sample Kincluded, among other phases, TiC and Ti₅ Si₃.

FIG. 6t is a fractograph taken at about 200× of the ceramic compositecoating 51 on the graphite substrate coupon 52 and corresponding toSample M. Results of x-ray diffraction analysis indicated that theconstituents in the area comprising the ceramic composite coating onSample M included, among other phases, TiC.

FIG. 6u is a fractograph taken at about 500× of the ceramic compositecoating 51 on the graphite substrate coupon 52 and FIG. 6v is aphotomicrograph taken at about 400× of the ceramic composite coating 51on the graphite substrate coupon 52 corresponding to Sample O. Resultsof x-ray diffraction analysis indicated that the constituent in the areacomprising the ceramic composite coating on Sample O included, amongother phases, TiC and Re.

                                      TABLE I                                     __________________________________________________________________________                                      Processing                                                                           Ceramic                                  Parent                        Time at                                                                              Composite                                Metal                                                                             Additive Powder                                                                         Thickness of                                                                           Processing                                                                           Processing                                                                           Coating                              Sample                                                                            Vapor                                                                             Size & Composition                                                                      Powder Coating                                                                         Temperature                                                                          Temperature                                                                          Thickness                            __________________________________________________________________________    A   Ti  -325                                                                              mesh TiC                                                                            178 μm                                                                              1900° C.                                                                      2 hours                                                                              150 μm                            B   Ti  1-5 μm TiB.sub.2                                                                      51 μm                                                                              1900° C.                                                                      2 hours                                                                              148 μm                            C   Ti  14.4                                                                              μm* SiB.sub.4                                                                     89 μm                                                                              1900° C.                                                                      2 hours                                                                              155 μm                            D   Ti  -325                                                                              mesh SiB.sub.6                                                                       64 μm                                                                              1900° C.                                                                      2 hours                                                                              140 μm                            E   Ti  12.6                                                                              μm* HfB.sub.2                                                                    102 μm                                                                              1900° C.                                                                      2 hours                                                                              157 μm                            F   Ti  -325                                                                              mesh WB                                                                              13 μm                                                                              1900° C.                                                                      2 hours                                                                              144 μm                            G   Ti  -325                                                                              mesh W.sub.2 B.sub.5                                                                 25 μm                                                                              1900° C.                                                                      2 hours                                                                              154 μm                            H   Ti  - 325                                                                             mesh TaB.sub.2                                                                       25 μm                                                                              1900° C.                                                                      2 hours                                                                              145 μm                            I   Ti  1-5 μm TiN                                                                            51 μm                                                                              1900° C.                                                                      2 hours                                                                              154 μm                            J   Ti  1-5 μm ZrN                                                                            64 μm                                                                              1900° C.                                                                      2 hours                                                                              153 μm                            K   Ti  -325                                                                              mesh Ti.sub.5 Si.sub.3                                                              229 μm                                                                              1900° C.                                                                      2 hours                                                                              176 μm                            L   Ti  1-5 μm TiSi.sub.2                                                                    140 μm                                                                              1900° C.                                                                      2 hours                                                                              178 μm                            M   Ti  1-5 μm MoSi.sub.2                                                                    165 μm                                                                              1900° C.                                                                      2 hours                                                                              254 μm                            N   Ti  -100                                                                              mesh Mo                                                                             241 μm                                                                              1900° C.                                                                      2 hours                                                                              610 μm                            O   Ti  -325                                                                              mesh Re                                                                             165 μm                                                                              1900° C.                                                                      2 hours                                                                              165 μm                            __________________________________________________________________________     *average particle diameter                                               

EXAMPLE 7

The following Example demonstrates a method for forming a reactionproduct coating on a graphite substrate by applying to the surface ofthe graphite substrate a parent metal powder and heating the powercovered graphite substrate in the presence of a parent metal vapor topermit the reaction between the parent metal powder, the metal vapor andthe graphite substrate. Table II contains a summary for Sample P, SampleQ, and Sample R of the parent metal powder size and composition, thethickness of the parent metal coating applied to graphite substratecoupon, and the ceramic composite coating thickness formed by placingthe parent metal powder coated graphite substrate coupon into the vapordeposition chamber at an elevated temperature.

The method of Example 1 was substantially repeated to prepare the GradeAXZ-5Q graphite substrate coupons for coating with a patent metal slurryand the method of Example 5 was substantially repeated to slurry coatthe substrate coupons with parent metal powders and to effect formationof the ceramic composite coatings on the graphite substrate coupons.

As with the Samples in Example 5 after the graphite substrate couponswere removed from the vapor deposition chamber, the ceramic compositecoated graphite substrate coupons were cut, mounted and polished forexamination using optical microscopy. Fracture surfaces of the ceramiccomposite coatings on the graphite substrate coupons were examined in anelectron microscope and x-ray diffraction analysis of the ceramiccomposite coatings was performed.

Specifically, FIG. 7a is a photomicrograph taken at about 500× of theceramic composite coating 51 on the graphite substrate coupon 52corresponding to Sample P. Results of x-ray diffraction analysisindicated that the constituents in the area comprising the ceramiccomposite coating on Sample P included, among other phases, TiC.

FIG. 7b is a fractograph taken at about 500× of the ceramic compositecoating 51 on the graphite substrate coupon 52 corresponding to SampleQ. Results of x-ray diffraction analysis indicated that the constituentsin the area comprising the ceramic composite coating on Sample Qincluded, among other phases, TiC, ZrC and Zr.

                  TABLE II                                                        ______________________________________                                                       Parent       Thickness                                                                             Ceramic                                          Parent  Metal        of      Composite                                        Metal   Size &       Powder  Coating                                   Sample Vapor   Composition  Coating Thickness                                 ______________________________________                                        P      Ti      -325 mesh Ti 432 μm                                                                             164 μm                                 Q      Ti      -325 mesh Zr 292 μm                                                                             151 μm                                 R      Ti      -325 mesh Hf 330 μm                                                                              86 μm                                 ______________________________________                                    

FIG. 7c is a fractograph taken at about 1000× of the ceramic compositecoating 51 on the graphite substrate 52 corresponding to Sample R.Results of x-ray diffraction analysis indicated that the constituents inthe area comprising the ceramic composite coating on Sample R included,among other phases, TiC, HfC, and C.

EXAMPLE 8

This Example demonstrates a method for forming a reaction productcoating on a graphite substrate with a complicated geometry by reactinga parent metal vapor with the graphite substrate at an elevatedtemperature.

The method of Example 1 was substantially repeated except that in placeof rectangular graphite substrate coupons, a threaded graphite rodmeasuring about 2.6 inches (66 mm) long, having an outer diameter ofabout 0.38 inches (9.6 mm) and about 17 threads per inch, and a graphitetube measuring about 3.2 inches (81 mm) long, having a outer diameter ofabout 1.3 inches (33 mm) and a wall thickness of about 0.125 inch (3.2mm) were used. The threaded graphite rod was held for about 5 hours atabout 1900° C. and the graphite tube was held for about 3 hours at about1900° C. within the vapor deposition chamber. At about room temperature,the threaded graphite rod and the graphite tube were removed from thevapor deposition chamber and it was observed that both were covered witha mirror like finish. Specifically, FIG. 8a is a photograph of thethreaded graphite rod as it appeared after removal from the vapordeposition chamber and FIG. 8b is a photograph of the graphite tube asit appeared after removal from the vapor deposition chamber.

EXAMPLE 9

The following Example demonstrates a method for forming a reactionproduct coating on a carbon-carbon composite substrate by reacting aparent metal vapor with the carbon-carbon composite substrate at anelevated temperature. Moreover, this Example demonstrates that theceramic composite coated carbon-carbon composite substrate can withstandextreme thermal shock conditions. The method of Example 1 wassubstantially repeated except that in addition to the graphite substratecoupon, a K-KARB® carbon-carbon composite (Kaiser Aerotech, San Leandro,Calif.) and a commercially available 4-D carbon-carbon composite wereplaced into the vapor deposition chamber. Additionally, the vapordeposition chamber was held for about 1 hour at about 1900° C. At aboutroom temperature, the carbon-carbon composite and the monolithicgraphite substrate coupons were removed from the lower chamber portionof the vapor deposition chamber and it was noted that a mirror likefinish coated the surface of the bodies.

To test the integrity of the ceramic composite coating on the 4-Dcarbon-carbon composite substrate, a thermal shock test was performed bysubjecting the ceramic composite coated 4-D carbon-carbon composite tothe flame of an oxyacetylene torch. Specifically, the ceramic compositecoated 4-D carbon-carbon composite was exposed to the flame of theoxyacetylene torch for about 15 seconds. The temperature rise in the 15second period was estimated to be from about room temperature to about3500° C. After subjecting the ceramic composite coated 4-D carbon-carboncomposite to the flame of the oxyacetylene torch for about 15 seconds,the ceramic coated carbon-carbon composite was allowed to cool for about30 seconds. The ceramic coated 4-D carbon-carbon composite was subjectedto four cycles comprised of 15 seconds of heating with the flame of theoxyacetylene torch followed by a 30 second air cooling. After theceramic composite coated carbon-carbon composite had cooled to aboutroom temperature, it was noted that the ceramic coating hadsubstantially maintained its integrity.

EXAMPLE 10

The following Example demonstrates a method for forming a reactionproduct coating on a carbon-carbon composite substrate by reacting aparent metal vapor with a carbon-carbon composite substrate coupon at anelevated temperature.

FIG. 9 is a cross-sectional schematic of the lay-up used to form aceramic composite coating on carbon-carbon composite substrate couponsas well as graphite substrate coupons. Specifically, FIG. 9 is across-sectional schematic of a vapor deposition chamber 130. The vapordeposition chamber 130 was comprised of a lower chamber portion 132,nine substrate support rods 133, attached to the sidewalls of the lowerchamber portion 132, nine parent metal source trays 134 within lowerchamber portion 132, an upper chamber portion 136, an extended portion137 containing a graphite felt 138 and attached to upper portion chamber136.

More specifically, the lower chamber portion 132 of the vapor depositionchamber 130 measured about 10 inches (254 mm) long, about 10 inches (254mm) wide, and about 4 inches (102 mm) high and had a wall thickness ofabout 0.5 inch (13 mm). The lower chamber portion 132 was machined froma piece of Grade AGSX graphite (Union Carbide Corporation, CarbonProduct Division, Cleveland, Ohio). The nine graphite support rods withdiameters of about 0.38 inch (9.6 mm) and made from Grade AGSX graphite(Union Carbide Corporation, Carbide Products Division, Cleveland, Ohio),were interference fit into holes in the sidewalls of lower chamberportion 132. All of the support rods were located about 2.0 inches (51mm) from the bottom of the lower chamber portion 132. Additionally, eachof the nine support rods were located about 1 inch (25 mm), about 2inches (51 mm), about 3 inches (76 mm), about 4 inches (102 mm), about 5inches (127 mm), about 6 inches (152 mm), about 7 inches (178 mm), about8 inches (203 mm), and about 9 inches (229 mm), respectively, from onesidewall of the lower chamber portion 132 and extended from one sidewallto the opposite sidewall of the lower chamber portion 132. The supportrods formed a supporting means for holding the graphite substratecoupons during coating.

The upper chamber portion 136 of the vapor deposition chamber 130measured about 10 inches (254 mm) long, about 10 inches (254 mm) wideand about 4 inches (102 mm) high and had a wall thickness of about 0.5inch (13 mm). The upper chamber portion 136 further included 5 holes 139having a diameter of about 0.25 inch (6.4 mm). The 5 holes 139, eachhaving a diameter of about 0.25 inch (6.4 mm), were substantiallycentrally located in the top portion of the upper chamber portion 136.The extended portion 137 measured about 3.5 inches (89 mm) long, 3.5inches (89 mm) wide, 2 inches (51 mm) high, and had a wall thickness ofabout 0.25 inch (6.4 mm). The extended portion 137 was also machinedfrom Grade AGSX graphite (Union Carbide Corporation, Carbon ProductDivision, Cleveland, Ohio) and was perforated with holes having adiameter of about 0.25 inch (6.4 mm) along the upper portion of thesidewalls and the top. A Grade GH graphite felt material 138 (FiberMaterials, Inc., Biddeford, Me.) was placed into the extended portion137 of the deposition chamber 130 and the extended portion 137 of thedeposition chamber 130 was aligned to the upper portion 136 of thedeposition chamber 130 with angles 140 made of graphite and secured tothe upper portion of the graphite chamber with graphite dowel pins 141.

The-parent metal source trays 134 were machined from Grade ATJ graphite(Union Carbide Corporation, Carbon Products Division, Cleveland, Ohio).The graphite metal source trays 134 measured about 2.5 inches (64 mm)long, 2.5 inches (64 mm) wide, 1 inch (25 mm) high and had a wallthickness of about 0.25 inch (6.4 mm). The graphite metal source trays104 were evenly placed in the space in the bottom of the lower chamberportion. All of the-graphite metal source trays were filled with about-5 mesh, +20 mesh (particle diameter between about 850 μm and 4000 μm)titanium, metal sponge (Micron Metals, Inc., Salt Lake City, Utah) to adepth ranging from about 0.25 inch (6.4 mm) to about 0.38 inch (9.7 mm).

A piece of Grade AXZ-5Q graphite material (Poco Graphite, Inc., Decatur,Tex.) measuring about 1 inch (25 mm) long, about 1 inch (25 mm) wide andabout 0.2 inch (5.1 mm) thick was sanded with 400 grit (average particlediameter of about 23 μm) silicon carbide paper to smooth the edges andthen with 1200 grit (average particle size of about 4 μm) siliconcarbide paper to smooth all surfaces. The sanded graphite substratecoupon was then cleaned for about 15 minutes in an ultrasonicallyagitated bath of acetone and dried in an air oven set at about 120° C.for about 0.45 hours. After drying substantially completely, thegraphite substrate coupon was placed on support rods 133 within thelower chamber portion 132. The same procedure was repeated with a pieceof K-KARB® carbon-carbon composite (Kaiser Aerotech, San Leandro,Calif.) and a commercially available 4-D carbon-carbon composite. Afterthe carbon-carbon composite components had dried for about 0.5 hours atabout 120 ° C., carbon-carbon composite coupons were placed on thegraphite support rods 133 within the lower chamber portion 132 of thevapor deposition chamber 130.

The upper portion 136 of the vapor deposition chamber 130 was placedonto and aligned with the lower chamber portion 132 of the depositionchamber 132. The vapor deposition chamber 130 and its contents were thenplaced into a vacuum furnace and the vacuum furnace door was closed. Thevacuum furnace was then evacuated to a pressure of about 0.2 millitorr.After about 50 minutes at a pressure of about 0.2 millitorr, the vacuumfurnace and its contents were heated to about 500° C. at about 250° C.per hour while maintaining a pressure less than about 60 millitorr. Thevacuum furnace was then heated from about 500° C. to about 1000° C. atabout 750° C. per hour while maintaining a pressure less than about 60millitorr. At about 1000° C., the pressure within the vacuum furnace wasallowed to increase to between about 60 millitorr and about 250millitorr and the vacuum furnace and its contents were heated from about1000 to about 1900° C. at about 750° C. per hour. After about 2 hours atabout 1900° C., with a pressure ranging from about 60 millitorr to about250 millitorr, the vacuum furnace and its contents were cooled at about900° C. per hour to about 1000° C. while maintaining a pressure rangingfrom about 60 millitorr to about 250 millitorr. The vacuum furnace andits contents were then cooled from about 1000° C. to about roomtemperature at about 125° C. per hour while maintaining a pressureranging from about 60 millitorr to about 250 millitorr.

At about room temperature, the vacuum furnace door was opened, the vapordeposition chamber 130 was removed from the furnace, disassembled andthe carbon-carbon composite and the monolithic graphite substratecoupons were removed from the lower chamber portion 132 of the vaporposition chamber 130. It was noted that a mirror like finish coated thesurface of the substrate coupons. Specifically, FIG. 10a is a comparisonof the graphite substrate coupon 80 and the ceramic composite coatedgraphite coupon 81 showing the change in appearance resulting from thecoating process. FIG. 10b is a photograph showing a comparison of theK-KARB® carbon-carbon composite coupon 90 and the ceramic coated K-KARB®carbon-carbon composite coupon 91 showing the change in appearanceresulting from the coating process. FIG. 10c is a photograph showing acomparison of the 4-D carbon-carbon composite coupon 100 and the ceramiccomposite coated 4-D carbon-carbon composite coupon 101 showing thechange in appearance resulting from the coating process.

EXAMPLE 11

The following Example demonstrates a method for forming a reactionproduct coating on a graphite substrate by applying to the surface of agraphite substrate an additive powder and heating the powder coveredsubstrate in the presence of a parent metal vapor to permit theincorporation of the additive powder in a ceramic composite coatingformed by the reaction between the parent metal vapor and the graphitesubstrate.

Table III contains a summary for Sample S through Sample Z of theadditive powder size and composition, the thickness of the additivepowder coating, the processing temperature to effect the formation ofthe ceramic composite coating, the processing time to effect theformation of the ceramic composite coating, and the thickness of theceramic composite coating on a graphite substrate coupon.

Specifically, the composition of the additive powders applied to thesurface of the graphite substrate as slurries included: Grade E67 1000grit (average particle diameter of about 5 μm) alumina (Norton Company,Worcester, Mass.), light powder magnesium oxide (Fisher Scientific,Pittsburgh, Pa.), about 1-5 μm particle diameter titanium dioxide(Atlantic Equipment Engineers, Bergenfield, N.J.), Grade MSZ zirconiumdioxide (Magnesium Electron, Inc., Flemmington, N.J.), about -325 mesh(particle diameter less than about 45 μm) magnesium aluminate spinel(Atlantic Equipment Engineers, Bergenfield, N.J.), about -325 mesh(particle diameter less than about 45 μm) silicon dioxide (ConsolidatedAstronautics, Inc., Saddle Brook, N.J.), tungsten dioxide (AlfaProducts, Morton Thiokol, Inc., Danvers, Mass.), molybdenum trioxide(AESAR®, Johnson Matthey, Seabrook, N.H.). The method of Example 1 wassubstantially repeated to prepare the Grade AXZ-5Q graphite substratecoupons (Poco Graphite, Inc., Decatur, Tex.) for slurry coating. Themethod of Example 10 was substantially repeated for Sample S throughSample Z in order to effect the formation of the ceramic compositecoating on the graphite substrate coupons.

                                      TABLE III                                   __________________________________________________________________________                                       Processing                                                                           Ceramic                                 Parent                         Time at                                                                              Composite                               Metal                                                                             Additive Powder                                                                          Thickness of                                                                           Processing                                                                           Processing                                                                           Coating                             Sample                                                                            Vapor                                                                             Size & Composition                                                                       Powder Coating                                                                         Temperature                                                                          Temperature                                                                          Thickness                           __________________________________________________________________________    S   Ti  1000 grit Al.sub.2 O.sub.3                                                               229 μm                                                                              1900° C.                                                                      2 hours                                                                              157 μm                           T   Ti  MgO        305 μm                                                                              1900° C.                                                                      2 hours                                                                              165 μm                           U   Ti  1-5 μm TiO.sub.2                                                                      102 μm                                                                              1900° C.                                                                      2 hours                                                                              178 μm                           V   Ti  ZrO.sub.2  102 μm                                                                              1900° C.                                                                      2 hours                                                                              166 μm                           W   Ti  -325 mesh MgAl.sub.2 O.sub.4                                                             229 μm                                                                              1900° C.                                                                      2 hours                                                                              152-174 μm                       X   Ti  -325 mesh SiO.sub.2                                                                      305 μm                                                                              1900° C.                                                                      2 hours                                                                              172 μm                           Y   Ti  WO.sub.2   216 μm                                                                              1900° C.                                                                      2 hours                                                                              174 μm                           Z   Ti  MoO.sub.3  330 μm                                                                              1900° C.                                                                      2 hours                                                                              163 μm                           __________________________________________________________________________

Fracture surfaces of the ceramic composite coatings on the graphitesubstrate coupons were examined using an electron microscope.Specifically, FIG. 11a is a fractograph taken at about 500× of theceramic composite coating 51 on the graphite substrate coupon 52corresponding to Sample S.

FIG. 11b is a fractograph taken at about 200× of the ceramic compositecoating 51 on the graphite substrate coupon 52 corresponding to SampleT.

FIG. 11c is a fractograph taken at about 200× of the ceramic compositecoating 51 on the graphite substrate coupon 52 corresponding to SampleX.

FIG. 11d is a fractograph taken at about 200× of the ceramic compositecoating 51 on the graphite substrate coupon 52 corresponding to SampleY.

FIG. 11e is a fractograph taken at about 200× of the ceramic compositecoating 51 on the graphite substrate 52 corresponding to Sample Z.

EXAMPLE 12

The following Example demonstrates a method for forming a ceramiccomposite body by heating a graphite material in the presence of aparent metal vapor to permit a reaction between the parent metal vaporand the graphite material.

Table IV contains summary for Sample AA through Sample AE of thesubstrate material, the metal vapor, the additive powder size andcomposition, the processing temperature and the processing time at theprocessing temperature for the formation of the ceramic compositematerials by this Example. Sample AA was MAGNAMITE™ 5 harness satinweave (HSW) graphite cloth (Hercules Aerospace, Magna, Utah) measuringabout 1 inch (25 mm) long, 1 inch (25 mm) wide and about 0.12 inch (3mm) thick. Sample AB was THORNEL® Grade VMA graphite mat (AmocoPerformance Products, Inc., Greenville, S.C.) measuring about 1.6 inches(41 mm) long, about 1.6 inches (41 mm) wide and about 1 inch (25 mm)thick. Sample AC was CALCARB™ rigid carbon fiber thermal insulation(Calcarb Inc., Willingboro, N.J.) measuring about 2.4 inches (61 mm)long, about 2.4 inches (61 mm) wide and about 0.05 inch (1.3 mm) thick.The carbon fiber thermal insulation had been impregnated with about 1.14grams of submicron boron powder (Callery Chemical Co., Callery, Pa.)using a vacuum impregnation technique. Specifically, a suspensioncomprised by weight of about 27.6% submicron boron powder (CalleryChemical Company, Callery, Pa.), 11.6% ELVACITE® 2045 acrylic resin (E.I. du Pont de Nemours & Co., Inc., Wilmington, Del.), 0.1% n-butylphthalate (Fischer Scientific Company, Pittsburgh, Pa.), 33.4% ethyleneglycol monobutyl ether (Textile Chemical Company, Reading, Pa.), andabout 27.3% isopropyl alcohol was made in a plastic jar. All thecomponents of the suspension, except for the boron powder, were combinedto make a solution. After all the components had substantiallycompletely dissolved to make a homogeneous solution, the boron powderwas added. The plastic jar was placed in a shaker mixer for about 15minutes, then on a roller mixer for at least 2 hours and finally placedinto an ultrasonically agitated bath to break apart any remainingagglomerates of boron powder and complete the formation of the boronsuspension. The boron suspension was poured into a dish. The carbonfiber thermal insulation was then submerged into the boron suspension toinitiate the impregnation with the boron powder. Once the carbon fiberthermal insulation remained submerged below the surface of the boronsuspension, the dish and its contents were moved to a vacuum chamber.After the vacuum chamber was closed, the vacuum chamber was evacuated toeffect the evaporation of a portion of the solvents from the boronsuspension. Air was then reintroduced into the vacuum chamber. Thecycles of evacuation and reintroduction of air were continued untilsubstantially all the solvents had evaporated and a boron powderimpregnated carbon fiber thermal insulation remained. Sample AD and AEwere CALCARB™ rigid carbon fiber thermal insulation measuring about 1.6inches (41 mm) long, 1.5 inches (38 mm) wide and about 1.3 inches thick.Sample AE was impregnated with about 0.83 grams of submicron boronpowder (Callery Chemical Co., Callery, Pa.) using the above-describedvacuum impregnation technique.

The method of Example 10 was substantially repeated to effect theformation of the ceramic composite materials with the exception thatSample AC was held at 1900° C. for about 6 hours. At about roomtemperature, the vapor deposition chamber was disassembled and thegraphite materials were removed from the bottom portion of the vapordeposition chamber to reveal that the titanium metal vapor had reactedwith the graphite materials to form highly reflective bodies.

                                      TABLE IV                                    __________________________________________________________________________                Parent                                                                            Additive        Processing Time                                   Substrate                                                                             Metal                                                                             Powder Size                                                                            Processing                                                                           at Processing                                 Sample                                                                            Material                                                                              Vapor                                                                             & Composition                                                                          Temperature                                                                          Temperature                                   __________________________________________________________________________    AA  5 HSW graphite                                                                        Ti  none     1900° C.                                                                      2 hours                                           fiber cloth                                                               AB  graphite mat                                                                          Ti  none     1900° C.                                                                      2 hours                                       AC  carbon fiber                                                                          Ti  submicron boron                                                                        1900° C.                                                                      6 hours                                           insulation                                                                AD  carbon fiber                                                                          Ti  none     1900° C.                                                                      2 hours                                           insulation                                                                AE  carbon fiber                                                                          Ti  submicron boron                                                                        1900° C.                                                                      2 hours                                           insulation                                                                __________________________________________________________________________

Additionally, results of x-ray diffraction analysis indicated that theconstituents of Sample AC comprised, among other phases, titaniumcarbide, titanium and titanium boride. FIG. 12 is a photomicrographtaken at about 400× corresponding to the ceramic composite body ofSample AC.

EXAMPLE 13

The following Example demonstrates a method for using a graphite bodythat has been coated with a ceramic composite coating by subjecting itto a parent metal vapor source.

A two-piece mold was used to make spherical platelet reinforcedcomposite bodies. FIG. 13 is a side view schematic of one piece of thetwo-piece mold. The halves of the two piece split mold were machinedfrom Grade ATJ graphite (Union Carbide Corporation, Carbon ProductsDivision, Cleveland, Ohio). The two-piece mold had an outer diameter ofabout 2.25 inches (57 mm), a height of about 3.7 inches (94 mm) and acomplex inner cavity. The inner cavity was comprised of a cylindricalvoid 153 having a diameter of about 1.9 inches (48 mm) and a height ofabout 0.75 inch (1.9 mm), a frustro-conical void 152 having a largediameter of about 1.9 inches (48 mm), a small diameter of about 0.7 inch(1.8 mm) and a height of about 1.2 inches (30 mm), and a spherical void151 having a diameter of about 1.4 inches (36 mm). The cylindrical void153, the frustro-conical void 152, and the spherical void 151 werealigned with the axis symmetry of the two-piece mold. Two grooves 155(one shown in FIG. 13), measuring about 0.031 inch (0.79 mm) wide andextending from the bottom of the two-piece mold to the spherical voidportion of the two-piece mold were located at about 0.13 inch from theaxis symmetry of the two-piece molds. Each half of the two-piece moldalso had two alignment holes 154 for receiving graphite rods having adiameter of about 1.3 inches and a length of about 1.1 inches. Matinghalves of the two-piece mold were assembled by applying GRAPHIBOND™551-R graphite glue (Aremco, Ossining, N.Y.) to mating surfaces andcontacting the coated mating surfaces. Assembled two-piece molds werethen placed in an air atmosphere oven set at about 120° C. for about 3hours to cure the graphite glue.

A vapor deposition chamber substantially the same as that in Example 1was used. Four assembled two-piece molds were placed into the lowerportion of a vapor deposition chamber. The large opening of thetwo-piece molds contacted the support rods and had a line of sight tothe parent metal source trays. The parent metal source trays within thevapor deposition chamber were filled with a nuclear grade zirconiumsponge material (Western Zirconium, Ogden, Utah) weighing about 75grams. The upper portion of the vapor deposition chamber was alignedwith the lower portion of the vapor deposition chamber and the vapordeposition chamber was placed onto a catch tray to form a lay-up. Thelay-up and its contents were then placed into a vacuum furnace and thevacuum furnace door was closed. The vacuum furnace was then evacuated toa pressure of about 0.2 millitorr. After about 50 minutes at a pressureof about 0.2 millitorr, the vacuum furnace and its contents were heatedto about 1000° C. at about 750° C. per hour. At about 1000° C., thepressure within the vacuum furnace was allowed to increase to betweenabout 60 millitorr to about 250 millitorr and the vacuum furnace and itscontents were heated from about 1000° C. to about 2000° C. at about 750°C. per hour. After about 5 hours at about 2000° C. with a pressureranging from about 60 millitorr to about 250 millitorr, the vacuumfurnace and its contents were cooled to about 1000° C. at about 1000° C.per hour and then from a 1000° C. to about room temperature at about125° C. per hour while maintaining a pressure ranging from about 60millitorr to about 250 millitorr. At about room temperature, the vacuumfurnace door was opened and the vapor deposition chamber wasdisassembled to reveal that the surface of two piece mold had beencoated by the deposition process.

The spherical cavity of the two-piece molds were then coated withTETRABOR® 1000 grit boron carbide (ESK Engineered Ceramics, New Canaan,Conn.). The coated two-piece molds were then tapped about 700 timesusing a tap volume meter (Model 2003 stampfvolumeter, J. EnglesmannA.G., West Germany) to settle the boron carbide. A parent metal ingotdesignated zirconium alloy 705, having a composition by weight of about<4.5% Hf, <0.2 Fe and Cu, <0.002% H, <0.025% N, <0.05% C, 2.0-3.0% Nb,<0.18% 0 and a minimum of 95.5% Zr and Hf, was placed onto the taploaded boron carbide powder. Several such setups were placed into agraphite containment boat to form a lay-up. The lay-up and its contentswere placed into a vacuum furnace and the vacuum furnace door wasclosed. The vacuum chamber was then evacuated to a pressure of about9×10⁻⁴ torr and then heated from about room temperature to about 1600°C. at about 600° C. per hour. At about 1600° C., the pressure within thevacuum furnace was allowed to increase to about 60 to 250 millitorrwhile the furnace was heated from about 1600° C. to about 2000° C. atabout 600° C. per hour. After about 30 minutes at about 2000° C. perhour, the vacuum pump to the furnace chamber was interrupted and argonwas introduced into the chamber at a flow rate of about 10 liters perminute until an over pressure of about 2 lbs per square inch (0.14kg/cm²) was achieved. The argon flow rate was then reduced to 2 litersper minute. After about 2 hours at about 2000° C. while maintaining anargon flow rate of about 2 liters per minute with an over pressure ofabout 2 lbs per square inch (0.14 kg/cm²), the furnace and its contentswere allowed to cool from about 2000° C. to about room temperature atabout 800° C. per hour. At about room temperature, the lay-up wasremoved from the furnace and it was noted that composite bodies hadformed by the reactive infiltration of the zirconium parent metal alloyinto the boron carbide powder and that the resultant ceramic compositebodies were easily removed from the coated two piece graphite molds.

A second group of four two-piece molds that had not been subjected tothe metal vapor treatment were filled with the boron carbide powder andsupplied with the zirconium parent metal alloy as described above. Thefilled two piece molds were placed onto a graphite containment tray andinto a vacuum furnace. The uncoated two piece molds were subjected tosubstantially the same processing cycle as the coated two piece molds,except that the furnace and its contents were cooled from about 2000° C.to about room temperature at about 600° C. per hour. At about roomtemperature, the two piece graphite molds were disassembled to revealthat the parent metal had preferentially wet the graphite mold andreacted with the inner surface of the graphite mold and leaked throughthe vents 155 within the graphite mold and minimized the amount ofreaction between the boron carbide and the zirconium parent metal. Thus,this Example demonstrates that the precoating of a graphite mold bysubjecting it to a vapor parent metal to form a coating on the moldimproves the ability to make dense ceramic composite bodies.

EXAMPLE 14

The following Example demonstrates that the formation of a titaniumcarbide reaction product coating on a graphite substrate by reacting aparent metal vapor with the graphite substrate at an elevatedtemperature not only improves the flexural strength of the resultantbody, but also increases the high temperature oxidation resistance ofthe resultant body. Table V summarizes the flexural strength ofas-received graphite substrate coupons and graphite substrate couponshaving a titanium carbide coating thereon, for two graphite substratematerials, as a function of test temperature.

The edges of graphite substrate coupons of Grade AXZ-5Q graphite (Poco,Inc., Decatur, Tex.) and Grade AXF-5Q graphite (Poco, Inc., Decatur,Tex.), measuring about 1.9 inches (48 mm) long, about 0.23 inch (5 mm)wide and about 0.11 inch (2.8 mm) thick, were toughened by sanding with1200 grit (average particle diameter of about 4 microns) silicon carbidepaper. The sanded graphite substrate coupons were then cleaned for about15 minutes in an ultrasonically agitated bath of acetone and dried forabout 15 minutes in a forced air oven set at about 120° C. After dryingsubstantially completely, the graphite substrate coupons were placedwithin a vapor deposition chamber substantially the same as thatdescribed in Example 10 to form a lay-up.

The lay-up and its contents were then placed into a vacuum furnace andthe vacuum furnace door was closed. The vacuum furnace was thenevacuated to a pressure of about 0.2 millitorr. The vacuum furnace andits contents were then heated to about 1000° C. at about 750° C. perhour while maintaining a pressure less than about 60 millitorr. At about1000° C., the pressure within the vacuum furnace was allowed in increaseto a pressure ranging between about 60 millitorr to about 250 millitorr.The vacuum furnace and its contents were then heated from about 1000° C.to about 1900° C. at about 750° C. per hour. After about 2 hours atabout 1900° C. with a pressure within the vacuum furnace chamber rangingbetween about 60 millitorr to about 250 millitorr, the vacuum furnaceand its contents were cooled at about 900° C. per hour to about 1000° C.and then from about 1000° C. to about room temperature at about 125° C.per hour while maintaining a pressure within the vacuum furnace chamberranging from about 60 millitorr to about 250 millitorr. At about roomtemperature, after the vacuum pump was turned off, the vacuum furnacewas allowed to adjust to atmospheric pressure and the lay-up and itscontents were removed from the furnace.

The flexural strength of the graphite substrate coupons with and withoutthe titanium carbide coating was measured using the procedure defined bythe Department of Army's proposed standard MIL-STD-1942A (Nov. 21,1983). This test was specifically designed for high temperature ceramicmaterials. The flexural strength is defined in this standard as themaximum outer fiber stress at the time of failure. A 41/4-flexural testwas used. The height and width of the test specimens were measured withthe precision of about 0.01 mm. The test specimens were subjected to astress applied at 4 points by two lower bearing points and two upperbearing points. The lower span bearing points were approximately 40millimeters apart and the upper span bearing points were approximately20 millimeters apart. The exact distances between the bearing pointswere determined and recorded for each individual flexural strengthmeasurement-with a precision of about 0.01 mm. The upper span wascentered over the lower span, so that the load was appliedsymmetrically. A constant displacement of about 0.02 inch/minute (0.5mm/minute) was exerted upon each sample until failure. The flexuralstrength measured at about room temperature was performed with a ModelCITS-20006 Universal Testing Machine (System Integration Technology,Inc., Straton, Mass.) equipped with a 5000 pound load cell (Model3132-149, Eaton Corp., Troy, Mich.). The flexural strength measured atabout 400° C., 600° C., 800° C. and 1000° C. was performed with a ModelCITS-2000/6W Universal Testing Machine (System Integration Technology,Inc., Straton, Mass.) equipped with a 500 pound load cell (Model3132-149, Eaton Corp., Troy, Mich.) and a resistance heated airatmosphere furnace (Series 3350, Applied Test Systems, Inc., Butler,Pa.). Samples that were used to determine flexural strengths at about400° C. and higher were held at the test temperature for at least 1hour.

Table V contains a summary of the results of the flexural strengthmeasurements conducted in an air atmosphere as a function of testtemperature. Specifically, the data in Table V show that the strength atroom temperature for the Grade AXZ-5Q graphite substrate couponsincreased from about 58.7 to about 127.4 megapascal (MPa) by forming atitanium carbide coating. In addition, the data in Table V show that theformation of a titanium carbide coating on the Grade AXZ-5Q carbonmaterial extends its oxidation resistance to at least 1000° C. That is,without the titanium carbide coating, the Grade AZX-5Q graphitesubstrate material oxidized at about 600° C., but with the titaniumcarbide coating, the material retained the flexural strength measured atroom temperature at about 1000° C. Improvements of high temperatureoxidation resistance were noted with the Grade AXF-5Q graphite substratematerial. That is, the

                                      TABLE V                                     __________________________________________________________________________    FLEXURAL STRENGTH MEASURED IN AN AIR ATMOSPHERE                               AS A FUNCTION OF TEMPERATURE                                                               Flexural Strength (MPa)                                          Material Tested                                                                            RT     400° C.                                                                       600° C.                                                                       800° C.                                                                       1000° C.                      __________________________________________________________________________    Grade AXZ-5Q Graphite                                                                      58.7 ± 5.8                                                                        61.4 ± 2.8                                                                        oxidized                                                                             --     --                                   Grade AXZ-5Q Graphite                                                                      127.4 ± 18.1                                                                      134.7 ± 17.4                                                                      116.2 ± 2.2                                                                       94.4 ± 3.8                                                                        56.9 ± 3.1                        with TiC Coating                                                              Grade AXF-5Q Graphite                                                                      95.2 ± 3.1                                                                        118.1 ± 9.1                                                                       oxidized                                                                             --     --                                   Grade AXF-5Q Graphite                                                                      115.9 ± 17.8                                                                      152.0 ± 38.7                                                                      141.7 ± 4.8                                                                       108.2 ± 11.7                                                                      --                                   with TiC Coating                                                              __________________________________________________________________________     titanium carbide coating extended the oxidation resistance of the Grade     AXF-3Q graphite substrate material beyond about 400° C. to about     800° C.

EXAMPLE 15

The following Example demonstrates that the formation of a reactionproduct coating on a graphite substrate by reacting a parent metal vaporwith a graphite substrate at an elevated temperature, improves thesurface quality of the resultant composite body, as compared to thestarting material. Specifically, Table VI contains a comparison of thesurface roughness of the starting graphite substrate coupon and the samegraphite substrate coupon coated with a reaction product which wasformed by subjecting the graphite substrate coupon to a parent metalvapor treatment at elevated temperatures for 2 hours, 4 hours and 6hours, respectively.

Three substrate coupons each being made of three different graphitematerials, namely, Grade AXZ-5Q graphite material (Poco, Inc., Decatur,Tex.), Grade AXF-5Q graphite material (Poco, Inc., Decatur, Tex.), GradeDFP-1 graphite material (Poco, Inc., Decatur, Tex.), Grade ATJ graphitematerial (Union Carbide Corporation, Carbon Products Division,Cleveland, Ohio) and Grade AGXS graphite material (Union CarbideCorporation, Carbon Products Division, Cleveland, Ohio), and eachmeasuring about 2 inches (51 mm) long, about 1 inch (25 mm) wide andabout 0.13 inch (3.2 mm) thick, were sanded with 1200 grit (averageparticle diameter of about 4 microns) silicon carbide paper. The sandedgraphite substrate coupons were then cleaned for about 15 minutes in anultrasonically agitated bath of acetone and dried for about 15 minutesin a forced air oven set about 120° C. After drying substantiallycompletely, the average surface roughness of the graphite substratecoupons were measured according the method described below and thegraphite substrate coupons were placed into a vapor deposition chambersubstantially the same as that described in Example 10 to form a lay-up.

The lay-up and its contents were then placed into a vacuum furnace andthe vacuum furnace door was closed. The vacuum furnace was thenevacuated to a pressure of about 0.2 millitorr. The vacuum furnace andits contents were then heated from about room temperature to about 1000°C. at about 750° C. per hour while maintaining a pressure less thanabout 60 millitorr. At about 1000° C., the pressure within the vacuumfurnace was increased to between about 60 millitorr and about 250millitorr and the vacuum furnace and its contents were heated from about1000° C. to about 1900° C. at about 750° C. per hour. After about twohours at about 1900° C., with a pressure within the vacuum chamberranging from about 60 millitorr to about 250 millitorr, the vacuumfurnace and its contents were cooled at about 900° C. per hour to about1000° C. The vacuum furnace and its contents were then cooled from about1000° C. to about room temperature at about 125° C. per hour whilemaintaining a pressure ranging from about 60 millitorr to about 250millitorr.

At about room temperature, the vacuum furnace door was opened and thevapor deposition chamber was removed from the furnace, disassembled andone titanium carbide coated graphite substrate coupon of each graphitematerial type was removed from the lower portion of the vapor depositionchamber and two graphite substrate coupons of each graphite materialtype remained in the lower portion of the vapor deposition chamber andwere subjected to the above described heating and treatment cycle asecond time. After the above-described cycle had once again beenrepeated, another series of titanium carbide coated graphite substratecoupons was removed from the lower portion of the vapor depositionchamber and the remaining five graphite substrate coupons were subjectedto the above described heating and treatment cycle a third time. Aftereach deposition cycle, it was noted that the graphite substrate couponshad a mirror-like finish. The surface roughness of each graphite couponprior to and following treatment according to this Example was measuredusing a TALYSURF 10 profilometer (Rank Taylor Hobson Limited, England).

The results of the average surface roughness measurements were comparedwith the preprocessed average surface roughness of the graphitesubstrate coupons. Those results are summarized in Table VI.Specifically, those results show that a decrease in average surfaceroughness as great as an order of magnitude can be attained by forming atitanium carbide reaction product coating on the surface of a graphitesubstrate coupon by the methods of this Example.

EXAMPLE 16

The following Example demonstrates that the formation of a titaniumcarbide reaction product coating on a graphite substrate coupon improvesthe ability of a graphite body to withstand thermal shock.

                                      TABLE VI                                    __________________________________________________________________________    SURFACE ROUGHNESS OF A FRICTION OF COATING TIME                               Average Surface Roughness (microinch)                                         Material     Starting Material                                                                      Treated for 2 hours                                                                     Treated for 4 hours                                                                     Treated for 6                       __________________________________________________________________________                                              hours                               Grade AXZ-5Q Graphite                                                                      13.1 ± 1.9                                                                          2.1 ± 0.5                                                                            --        --                                  Grade AXZ-5Q Graphite                                                                      13.1 ± 1.1                                                                          --        1.9 ± 0.8                                                                            --                                  Grade AXZ-5Q Graphite                                                                      15.6 ± 2.4                                                                          --        --        1.0 ± 0.1                        Grade AXF-5Q Graphite                                                                      47.2 ± 4.8                                                                          4.0 ± 0.9                                                                            --        --                                  Grade AXF-5Q Graphite                                                                      13.2 ± 0.4                                                                          --        1.7 ± 0.7                                                                            --                                  Grade AXF-5Q Graphite                                                                      11.5 ± 0.9                                                                          --        --        1.1 ± 0.4                        Grade DFP-1 Graphite                                                                       14.1 ± 2.0                                                                          1.7 ± 0.2                                                                            --        --                                  Grade DFP-1 Graphite                                                                       15.4 ± 1.2                                                                          --        1.6 ± 0.3                                                                            --                                  Grade DFP-1 Graphite                                                                       12.8 ± 1.4                                                                          --        --        0.8 ± 0.1                        Grade ATJ Graphite                                                                         24.4 ± 7.6                                                                          8.0 ±  1.9                                                                           --        --                                  Grade ATJ Graphite                                                                         23.8 ± 7.6                                                                          --        5.3 ± 1.4                                                                            --                                  Grade ATJ Graphite                                                                         18.9 ± 3.9                                                                          --        --        4.3 ± 1.2                        Grade AGSX Graphite                                                                        67.0 ± 6.8                                                                          26.0 ± 5.9                                                                           --        --                                  Grade AGSX Graphite                                                                        107.0 ± 29.4                                                                        --        15.0 ± 4.5                                                                           --                                  Grade AGSX Graphite                                                                        209.0 ± 36.0                                                                        --        --        15.8 ± 4.7                       __________________________________________________________________________

Pieces of Grade AXZ-5Q graphite material (Poco, Inc., Decatur, Tex.),measuring about 1.9 inches (48 mm) long, about 0.23 inch (5.8 mm) wideand about 0.11 inch (2.8 mm) thick were sanded with 1200 grit (averageparticle diameter of about 4 microns) silicon carbide paper. Pieces ofK-KARB® carbon-carbon composite material (Kaiser Aerotech, San Leandro,Calif.) measuring about 2 inches (51 mm) long, about 0.24 inch (6.1 mm)wide and about 0.12 inch (3 mm) thick were first sanded with 400 grit(average particle diameter of about 23 μm) and then with 1200 grit(average particle diameter of about 4 μm) silicon carbide paper. Thesanded graphite substrate coupons were then cleaned for about 15 minutesin an ultrasonically agitated bath of acetone and dried for about 15minutes in a forced air oven set at about 120° C. After dryingsubstantially completely, the graphite substrate coupons were placed onsupport rods within the lower chamber portion of a vacuum depositionchamber substantially the same as that described in Example 10 to form alay-up.

The lay-up and its contents were then placed into a vacuum furnace andthe vacuum furnace door was closed. The vacuum furnace was thenevacuated to a pressure of about 0.2 millitorr. The vacuum furnace andits contents were then heated to about 1000° C. at a rate of about 750°C. per hour while maintaining a pressure less than about 60 millitorr.At about 1000° C., the pressure within the vacuum furnace was allowed toincrease to between about 60 millitorr to about 250 millitorr. Thevacuum furnace and its contents were then heated from about 1000° C. toabout 1900° C. at about 750° C. per hour. After about 2 hours at about900° C. with a pressure within the vacuum furnace chamber rangingbetween about 60 millitorr and about 250 millitorr, the vacuum furnaceand its contents were cooled at about 900° C. to about 1000° C. and thenfrom about 1000° C. to about room temperature at about 125° C. per hourwhile maintaining a pressure within the vacuum furnace chamber rangingfrom about 60 millitorr to about 250 millitorr. At about roomtemperature, after the vacuum pump had been turned off, the vacuumfurnace was allowed to adjust to about atmospheric pressure and thelay-up and it contents were removed from the furnace.

Several bars of the titanium carbide coated Grade AZX-5Q graphitematerial and the K-KARB® carbon-carbon composite material were set asidewhile others were subjected to a thermal shock test performed bysubjecting the ceramic composite coated bodies to the flame of anoxyacetylene torch. Specifically, the coated bodies were exposed to theflame of an oxyacetylene torch for about 15 seconds. The temperaturerise in the 15-second period was estimated to be from about roomtemperature to about 3500° C. After subjecting the ceramic compositecoated bodies to the flame of the oxyacetylene torch for about 15minutes, the coated bodies were allowed to cool to room temperature.

The method of Example 14 was substantially repeated to measure theflexural strength of the thermally shocked and non-thermally coatedshocked uncoated bodies.

The results of the flexural strength measurements for the coated anduncoated bodies in the as received and thermally shocked conditions aresummarized in Table VII. Specifically, Table VII shows that theformation of a titanium carbide coating on a Grade AXZ-5Q graphite bodyby the methods of this Example can improve the flexural strength of athermally shocked body from about 40.4 megapascal to about 80.8megapascal. The flexural strength of a coated thermally shocked K-KARB®carbon-carbon composite body can be improved from about 105.1 MPa toabout 124 MPa.

EXAMPLE 17

The following Example demonstrates, among other things, a method forforming a reaction product coating on a variety of graphite substratesby reacting a parent metal vapor with the graphite substrate bodies atan elevated temperature. Specifically, the following Exampledemonstrates a method for forming a titanium carbide reaction productcoating on a variety of graphite substrate bodies. More specifically,Table VIII sets forth the specific graphite substrate grades andsources, the sample weights prior to and after coating, the sampleweight gains after coating, and the dimensions of the large and smalldiameters of each sample after coating for each of the coated graphitesubstrate bodies identified as Samples AF through AW.

FIG. 14 is a cross-sectional schematic of a lay-up used in this Exampleto form reaction product coatings on a variety of graphite substratebodies. Specifically, FIG. 14 is a cross-sectional schematic of a vapordeposition chamber 1401. The vapor deposition chamber 1401 was comprisedof a lower chamber portion 1402, a parent metal source tray 1414 withinthe lower chamber portion 1402, a sample-support rack 1418, attached tothe parent metal source tray 1414 by support rods 1417, an

                  TABLE VII                                                       ______________________________________                                        COMPARISON OF FLEXURAL STRENGTH                                               PRIOR TO AND FOLLOWING THERMAL SHOCK                                          Flexural Strength (MPa)                                                                            K-KARB ® Carbon-                                     Grade AXZ-5Q Graphite                                                                              Carbon Composite                                         Uncoated      Coated     Uncoated  Coated                                     ______________________________________                                        As      58.7 ± 5.8                                                                           127.4 ± 18.1                                                                          123.7 ± 0.8                                                                        120.7 ± 2.3                           Received                                                                      Thermally                                                                             43.4 ± 6.9                                                                            80.8 ± 16.7                                                                          105.1 ± 4.9                                                                        124.4 ± 0.5                           Shocked                                                                       ______________________________________                                    

upper chamber portion 1403, a parent metal vapor trap 1421 containing agraphite felt 1409 and a graphite fiber board 1410 and attached to upperportion chamber 1403.

More specifically, the lower chamber portion 1402 of the vapordeposition chamber 1401 measured about 17.5 inches (445 mm) long, about11.5 inches (292 mm) wide, about 8 inches (203 mm) high and had a wallthickness of about 0.5 inch (13 mm). The lower chamber portion 1402 wasmachined from a piece of Grade AGSX graphite (Union Carbide Corporation,Carbon Product Division, Cleveland, Ohio). An engagement rail 1405having a cross section measuring about 1.5 inches (38 mm) long and about0.25 inch (6.3 mm) wide was attached to the inner surface and along thetop of the Rower chamber portion 1402 so as to extend about 0.5 inch (13mm) beyond the top of the lower chamber portion 1402.

The upper chamber portion 1403 of the vapor deposition chamber 1401measured about 17.5 inches (445 mm) long, about 11.5 inches (292 mm)wide, about 8 inches (203 mm) high and had a wall thickness of about 0.5inch (13 mm). The upper chamber portion 1403 further included a parentmetal vapor trap 1421 which facilitated the communication between theatmosphere of a vacuum furnace and the atmosphere within the vapordeposition chamber 1401 while preventing the parent metal vapor fromescaping into the vacuum furnace. The parent metal vapor trap 1421incorporated thirteen communication holes 1413 (only four are depictedin FIG. 14) through and centrally located in the top of the upperchamber portion 1403. Five of the communication holes 1413 had adiameter of about 0.43 inch (11 mm) while the remaining eightcommunication holes 1413 had a diameter of about 0.25 inch (6.4 mm). Anupper extended portion 1407 of the parent metal vapor trap 1421 measuredabout 6.0 inches (152 mm) long, 6.0 inches (152 mm) wide, 0.5 inch (13mm) high, and had a wall thickness of about 0.25 inch (6.4 mm). Theupper extended portion 1407 was machined from Grade AGSX graphite (UnionCarbide Corporation, Carbon Product Division, Cleveland, Ohio). Severalpieces of Grade GH graphite felt material 1409 (Fiber Materials, Inc.,Biddeford, Me.) were placed into and filled the cavity of the upperextended portion 1407 of the parent metal vapor trap 1421. A lowerextended portion 1408 of the parent metal vapor trap 1421 measured about6.0 inches (152 mm) long, 6.0 inches (152 mm) wide, 0.5 inch (13 mm)high, and had a wall thickness of about 0.25 inch (6.4 mm). The lowerextended portion 1408 was also machined from Grade AGSX graphite (UnionCarbide Corporation, Carbon Product Division, Cleveland, Ohio).Fifty-two holes (only two depicted in FIG. 14) having an about 0.19 inch(4.8 mm) diameter were substantially equally spaced along the top andperimeter of lower extended portion 1408. A Grade 2300 G-BOARD® graphitefiber board 1410 (Materials Unlimited, Inc., Templeton, Mass.) wasplaced into and filled the cavity of the lower extended portion 1408 ofthe parent metal vapor trap 1421. The parent metal vapor trap 1421 wascompleted by fastening both the upper extended portion 1407 and lowerextended portion 1408 over the communication holes 1413 through the topof the upper portion 1403 with four threaded graphite rods 1411, eachhaving a diameter of about 0.25 inch (6.4 mm) and secured to the upperportion 1403 with graphite nuts 1412. A engagement rail receptor 1406having a cross-section measuring about 0.63 (16 mm) wide and about 2.25inches (57 mm) long was attached to the inner surface and along thebottom of the upper chamber portion 1403. A portion of the engagementrail receptor 1406 was cut out so that the engagement rail 1405 wouldfit into the cutout portion as depicted in FIG. 14.

The parent metal source tray 1414 was machined from Grade AGSX graphite(Union Carbide Corporation, Carbon Products Division, Cleveland, Ohio).The parent metal source tray 1414 measured about 16 inches (406 mm)long, 10 inches (254 mm) wide, 1 inch (25 mm) high and had a five byeight array of holes 1415 each having a diameter of about 1.5 inches (38mm) and a depth of about 0.5 inch (13 mm). Additionally, the forty holes1415 in the graphite metal source tray 1414 were approximately evenlyspaced. The forty holes 1415 in the graphite metal source tray 1414 werefilled with parent metal powder 1416 comprised of about -5 mesh, +20mesh (particle diameter between about 850 μm and 4000 μm) titanium metalsponge (Micron Metals, Inc., Salt Lake City, Utah) to a depth rangingfrom about 0.25 inch (6.4 mm) to about 0.5 inch (13 mm).

The sample support rack 1418 was attached to the parent metal sourcetray 1414 by eight support rods 1417 (only four are depicted in FIG.14). The sample support rack, machined from Grade ATJ graphite (UnionCarbide Corporation, Carbon Products Division, Cleveland, Ohio),measured about 9.75 inches (248 mm) long, about 5 inches (127 mm) wide,about 1 inch (25 mm) high and had a wall thickness of about 0.5 inch (13mm). The eight support rods 1417, machined from Grade AGSX graphite(Union Carbide Corporation, Carbon Products Division, Cleveland, Ohio),measured about 2 inches (51 mm) long and had an about 0.25 (6.4 mm)diameter.

The upper portion 1403 of the vapor deposition chamber 1401 was placedonto, and aligned with, the lower chamber portion 1402 of the depositionchamber 1401 so that engagement rail 1405 fit into the cut-out portionsof engagement rail receptor 1406 to create a seal for the parent metalvapor. The vapor deposition chamber 1401, containing the parent metalpowder 1416 in the graphite source tray 1414, was then placed into avacuum furnace and the vacuum furnace door was closed. The vacuumfurnace was then evacuated to a pressure of about 0.2 millitorr. Afterabout 50 minutes at a pressure of about 0.2 millitorr, the vacuumfurnace and its contents were heated to about 1900° C. at about 750° C.per hour while maintaining a pressure of about 0.2 millitorr. Afterabout 2 hours at about 1900° C., with a pressure of about 0.2 millitorr,the vacuum furnace and its contents were cooled at about 900° C. perhour to about 1000° C. while maintaining a pressure of about 0.2millitorr. The vacuum furnace and its contents were then cooled fromabout 1000° C. to about room temperature at about 125° C. per hour whilemaintaining a pressure of about 0.2 millitorr. This process was repeatedtwo more times.

Eighteen graphite bodies 1420 (only seven are depicted in FIG. 14), aslisted in Table VIII, having a machined surface finish and a firstportion having a diameter of about 0.739 inch (18.8 mm) and a height ofabout 0.23 inch (5.8 mm) and a second portion having a diameter of about0.497 inch (12.6 mm) and an average height of about 0.23 (5.8 mm) andconcentrically aligned with and extending from the first portion, werecleaned for about 15 minutes in an ultrasonically agitated bathcomprised by weight of about 50% ethanol and about 50% deionized waterand dried in an air oven set at about 120° C. for about 0.33 hours(i.e., until weight losses due to heating at about 120° C. ceased).After drying substantially completely, the graphite substrate bodies1420 were placed on a graphite support tray 1419 so that the firstportion of each graphite substrate body 1420 contacted the graphitesupport ray 1419. The graphite support tray 1419 supporting the graphitesubstrate bodies 1402 was then placed on the support frame 1418 withinthe lower chamber portion 1402.

After the titanium parent metal 1416 had been replenished within theparent metal source tray 1414, the upper portion 1403 of the vapordeposition chamber 1401 was again placed onto and aligned with the lower

                                      TABLE VIII                                  __________________________________________________________________________                                     Large Small                                                                   Diameter                                                                            Diameter                                                  Sample   Sample                                                                             (inches)                                                                            (inches)                                                  Weight (grams)                                                                         Weight                                                                             Dimension                                                                           Dimension                                                 Coating  Grain                                                                              after after                                  Sample                                                                            Graphite Grade, Source                                                                       Prior to                                                                           After                                                                             (grams)                                                                            Coating                                                                             Coating                                __________________________________________________________________________    AF  AXF-5Q, Poco Graphite                                                                        4.93 5.65                                                                              0.72 0.749 0.507                                      Inc., Decature, TX                                                        AG  AXF-5Q, Poco Graphite                                                                        4.90 5.61                                                                              0.71 0.748 0.507                                      Inc., Decature, TX                                                        AH  ZXF-5Q, Poco Graphite                                                                        4.79 5.50                                                                              0.71 0.748 0.506                                      Inc., Decature, TX                                                        AI  ZXF-5Q, Poco Graphite                                                                        4.78 5.49                                                                              0.71 0.747 0.506                                      Inc., Decature, TX                                                        AJ  TM, Poco Graphite                                                                            4.95 5.65                                                                              0.70 0.748 0.506                                      Inc., Decature, TX                                                        AK  TM, Poco Graphite                                                                            4.91 5.63                                                                              0.72 0.748 0.506                                      Inc., Decature, TX                                                        AL  2020, Stackpole Carbon Co.,                                                                  4.70 5.37                                                                              0.67 0.748 0.506                                      St. Marys, PA                                                             AM  2020, Stackpole Carbon Co.,                                                                  4.70 5.40                                                                              0.70 0.748 0.506                                      St. Marys, PA                                                             AN  G347, Tokai Carbon America,                                                                  5.03 5.73                                                                              0.70 0.748 0.507                                      Inc., New York, NY                                                        AO  G347, Tokai Carbon America,                                                                  5.02 5.72                                                                              0.70 0.748 0.506                                      Inc., New York, NY                                                        AP  G520, Tokai Carbon America,                                                                  5.03 5.72                                                                              0.69 0.748 0.506                                      Inc., New York, NY                                                        AQ  G520, Tokai Carbon America,                                                                  5.01 5.69                                                                              0.68 0.748 0.506                                      Inc., New York, NY                                                        AR  ATJ, Union Carbide, Carbon                                                                   4.69 5.38                                                                              0.69 0.748 0.506                                      Products Division, Cleveland,                                                 OH                                                                        AS  ATJ, Union Carbide, Carbon                                                                   4.73 5.40                                                                              0.67 0.748 0.506                                      Products Division, Cleveland,                                                 OH                                                                        AT  ZTA, Union Carbide, Carbon                                                                   5.14 5.83                                                                              0.69 0.749 0.507                                      Products Division, Cleveland,                                                 OH                                                                        AU  ZTA, Union Carbide, Carbon                                                                   5.15 5.86                                                                              0.71 0.748 0.507                                      Products Division, Cleveland,                                                 OH                                                                        AV  AGSX (G-10), Union Carbide,                                                                  4.67 5.36                                                                              0.69 0.748 0.506                                      Carbon Products Division,                                                     Cleveland, OH                                                             AW  AGSX (G-10), Union Carbide,                                                                  4.65 5.34                                                                              0.69 0.748 0.506                                      Carbon Products Division,                                                     Cleveland, OH                                                             __________________________________________________________________________

chamber portion 1402 of the deposition chamber 1401. The vapordeposition chamber 1401 and its contents were then placed into a vacuumfurnace and the vacuum furnace door was closed. The vacuum furnace wasthen evacuated to a pressure of about 0.2 millitorr. After about 50minutes at a pressure of about 0.2 millitorr, the vacuum furnace and itscontents were heated to about 1900° C. at about 750° C. per hour. Afterabout 2 hours at about 1900° C., with a pressure of about 0.2 millitorr,the vacuum furnace and its contents were cooled at about 900° C. perhour to about 1000° C. while maintaining a pressure of about 0.2millitorr. The vacuum furnace and its contents were then cooled fromabout 1000° C. to about room temperature at about 125° C. per hour whilemaintaining a pressure of about 0.2 millitorr.

At about room temperature, the vacuum furnace door was opened, the vapordeposition chamber 1401 was removed from the furnace, disassembled andthe eighteen graphite substrate bodies 1420 were removed from the lowerchamber portion 1402 of the vapor position chamber 1401. It was notedthat a mirror-like finish coated the surface of the graphite substratebodies 1420. Further, as summarized in Table VIII, the graphite bodies1420 experienced weight gains and diameter increases relative to thoseparameters prior to exposure to the titanium parent metal-vapor cloudwithin the vapor deposition chamber 1401.

Thus, this Example demonstrates that the methods of the Example arecompatible with a variety of graphite substrate bodies.

EXAMPLE 18

The following Example demonstrates a method for forming a reactionproduct coating on a graphite substrate coupon by reacting a parentmetal vapor with the graphite substrate coupon at an elevatedtemperature. Specifically, this Example demonstrates a method forforming a silicon carbide coating on various graphite substrate couponsby reacting a silicon parent metal vapor with the various carbonsubstrate coupons at an elevated temperature.

The grades and sources of the graphite substrate coupons used in thisExample include: Grade AXF-5Q graphite (Poco Graphite Inc., Decature,Tex.), Grade TM graphite (Poco Graphite Inc., Decature, Tex.), Grade ATJgraphite (Union Carbide Corporation, Carbon Products Division,Cleveland, Ohio), Grade H490 graphite (Great Lakes Carbon Corporation,Morgantown, N.C.), and Grade AGSX graphite (Union Carbide Corporation,Carbon Products Division, Cleveland, Ohio). The graphite substratecoupons made from the Grade AXF-5Q and Grade TM graphite measured about1 inch (25 mm) square and about 0.13 inch (33 mm) thick while thegraphite substrate coupons made from the Grade ATJ graphite, Grade H490graphite, and Grade AGSX graphite measured about 1 inch (25 mm) squareand about 0.24 inch (6.1 mm) thick. Each of the graphite substratecoupons was prepared for coating by first placing the coupons in aultrasonic bath containing a solution comprised by weight of about 50%ethanol and about 50% deionized water for about 15 minutes. After thegraphite substrate coupons were removed from the ultrasonic bath, thegraphite substrate coupons were dried in air at about room temperaturefor about 5 minutes. The graphite substrate coupons were then placedinto an oven, set at about 120° C. and their weight was monitored untilthere was substantially no weight change. Typically, the graphitesubstrate coupons exhibited no weight change after about 7 minutes atabout 120° C. After drying substantially completely, the graphitesubstrate coupons were placed on the support rods within the lowerchamber portion of a vapor deposition chamber, which was configuredsubstantially the same as that described in Example 10 except that theparent-metal source tray contained silicon parent metal instead oftitanium parent metal.

The upper chamber portion of the vapor deposition chamber was placedinto and aligned with the lower portion of the deposition chamber. Thevapor deposition chamber and its contents were then placed into a vacuumfurnace and the vacuum furnace door was closed. The vacuum furnace wasthen evacuated to a pressure of about 0.2 millitorr. After about 50minutes at a pressure of about 0.2 millitorr, the vacuum furnace and itscontents were heated to about 1500° C. at about 500° C. per hour whilemaintaining a pressure of about 0.2 millitorr. After about 2 hours atabout 1500° C. with a pressure of about 0.2 millitorr, the vacuumfurnace and its contents were cooled to about room temperature at about500° C. per hour while maintaining a pressure of about 0.2 millitorr.

At about room temperature, the vacuum furnace door was opened, the vapordeposition chamber was removed from the furnace, disassembled, and thegraphite substrate coupons were removed from the lower chamber portionof the vapor deposition chamber. It was noted that the surface finish ofthe graphite substrate coupons had changed because the surfaces had beensubjected to and had reacted with a parent metal vapor cloud comprisingsilicon metal to form a reaction product according to the Example.

Thus, this Example demonstrates that the surfaces of a variety ofgraphite substrate coupons may be altered by subjecting the graphitesubstrate coupons to a silicon parent metal cloud.

EXAMPLE 19

The following Example demonstrates, among other things, a method forforming a reaction product coating on a graphite substrate coupon byreacting a parent metal vapor with a graphite substrate coupon at anelevated temperature. Specifically, the following Example demonstrates amethod for forming a niobium carbide reaction product coating on agraphite substrate coupon by reacting a niobium parent metal vapor witha graphite substrate coupon at an elevated temperature.

FIG. 15 is a cross-sectional schematic of the lay-up used in thisExample to form a reaction product coating on a graphite substratecoupon. Specifically, FIG. 15 shows a vapor deposition chamber 1501comprising a lower chamber portion 1502, a parent metal source tray 1514within lower chamber portion 1502, a sample support rack 1515, extendingfrom the parent metal source tray 1514, an upper chamber portion 1503, aparent metal vapor trap 1508 containing a graphite felt 1509 andattached to upper portion chamber 1503.

More specifically, the lower chamber portion 1502 of the vapordeposition chamber 1501 measured about 3 inches (76 mm) square, about 4inches (102 mm) high and had a wall thickness of about 0.25 inch (6.4mm). The lower chamber portion 1502 was machined from a piece of GradeATJ graphite (Union Carbide Corporation, Carbon Product Division,Cleveland, Ohio). An alignment rail 1505 measuring about 7 inches (178mm) long, about 1 inch (25 mm) wide, and about 0.25 inch (6.3 mm) thickwas attached to the outer surface and along one side of the lowerchamber portion 1502 so as to extend about 3 inches (76 mm) beyond thetop of the lower chamber portion 1502. The alignment rail 1505 wasattached to the lower chamber portion 1502 with a threaded graphite rodhaving a diameter of about 0.25 inch (6.4 mm).

The upper chamber portion 1503 of the vapor deposition chamber 1501measured about 3 inches (76 mm) square, about 2 inches (51 mm) high andhad a wall thickness of about 0.25 inch (6.4 mm). The upper chamberportion 1503 further included a parent metal vapor trap 1508 whichfacilitated the communication between the atmosphere of a vacuum furnacewith the atmosphere within the vapor deposition chamber 1501, whilepreventing the parent metal vapor from escaping into the vacuum furnace.The parent metal vapor trap 1508 incorporated five communication holes1511 (only two are depicted in FIG. 15) through and centrally located inthe top of the upper chamber portion 1503. The communication holes 1511had a diameter of about 0.31 inch (8 mm). A top plate 1509 of the parentmetal vapor trap 1508 measured about 2.5 inches (64 mm) long, 2.5 inches(64 mm) wide, and 0.25 inch (6.4 mm) thick. The top plate 1509 wasmachined from Grade ATJ graphite (Union Carbide Corporation, CarbonProduct Division, Cleveland, Ohio). A Grade GH graphite felt material1510 (Fiber Materials, Inc., Biddeford, Me.) having a thickness of about0.13 inch (3.3 mm) was placed between the top plate 1509 of the parentmetal vapor trap 1508 and the top of the upper chamber portion 1503.Additionally, a threaded rod 1512 extended from one side, as shown, ofthe upper chamber portion 1503 to secure the upper chamber portion 1503to the alignment rail 1515 of the lower chamber portion 1502, by using anut 1513.

The parent metal source tray 1514 was machined from Grade ATJ graphite(Union Carbide Corporation, Carbon Products Division, Cleveland, Ohio).The parent metal source tray 1514 measured about 2 inches (51 mm)square, about 1 inch (25 mm) high at two opposite ends, about 4 inches(102 mm) high at the remaining two opposite ends and had a wallthickness of about 0.25 inch (6.4 mm). The sample support rack 1515comprised the two 4 inch (102 mm) walls of the parent metal source tray1514 and had a through hole 1517 for receiving a support rod 1516. Thecavity in the graphite metal source tray 1514 was filled with parentmetal powder 1519 comprising about -325 mesh, (particle diameter lessthan about 45 μm) niobium metal (Atlantic Equipment Engineers,Bergenfield, N.J.) and weighing about 137 grams.

A graphite substrate coupon 1518 measuring about 1.5 inches (38 mm)square and about 0.25 inch (6.4 mm) which was cleaned for about 15minutes in an ultrasonically agitated bath comprising by weight about50% ethanol and about 50% deionized water. After removal from theultrasonically agitated bath, the graphite substrate coupon 1518 wasdried at about room temperature for about 5 minutes and thensubstantially completely dried in an air oven set at about 120° C. forabout 7 minutes (i.e., until weight losses due to drying at about 120°C. substantially ceased). After drying substantially completely, thegraphite substrate coupon 1518 was placed on a support rod 1516. Thegraphite support rod 1516 with the graphite substrate body 1518 was thenplaced on the support frame 1515 of the parent metal source tray 1514within the lower chamber portion 1502.

The upper portion 1503 of the vapor deposition chamber 1501 was placedonto, aligned with and secured to the lower chamber portion 1502 of thedeposition chamber 1501. The vapor deposition chamber 1501 and itscontents were then placed into a vacuum furnace and the vacuum furnacedoor was closed. The vacuum furnace was then evacuated to a pressure ofabout 0.2 millitorr. After about 60 minutes at a pressure of about 0.2millitorr, the vacuum furnace and its contents were heated to about2250° C. at about 750° C. per hour. After about 4 hours at about 2250°C., with a pressure of about 0.2 millitorr, the vacuum furnace and itscontents were cooled at about 1000° C. per hour to about 1000° C. whilemaintaining a pressure of about 0.2 millitorr. The vacuum furnace andits contents were then cooled from about 1000° C. to about roomtemperature at about 125° C. per hour while maintaining a pressure ofabout 0.2 millitorr.

At about room temperature, the vacuum furnace door was opened, the vapordeposition chamber 1501 was removed from the furnace, disassembled andthe graphite substrate coupon 1518 were removed from the lower chamberportion 1502 of the vapor position chamber 1501. It was noted that thesurface of the graphite substrate coupon 1518 possessed a mat-likefinish. Thus, this Example demonstrates that the surface of a graphitesubstrate coupon may be altered by subjecting the surface to a niobiumparent metal cloud according to the method of the present invention.

EXAMPLE 20

The following Example demonstrates, among other things, a method forforming a reaction product coating on a graphite substrate coupon byreacting a parent metal vapor with a graphite substrate coupon at anelevated temperature. Specifically, the following Example demonstrates amethod for forming a hafnium carbide reaction product coating on agraphite substrate coupon by the methods of the present invention.

FIG. 16a is a cross-sectional schematic of the lay-up used in thisExample to form a reaction product coating on a graphite substratecoupon. Specifically, FIG. 16a shows a vapor deposition chamber 1601comprising a lower chamber portion 1602, a slotted parent metal supportmember 1608 within the lower chamber portion 1602, a sample support rack1613 attached to the slotted parent metal support member 1608 by supportrods 1612, an upper chamber portion 1603, a parent metal vapor trap 1604containing a graphite felt 1621 and attached to the top of upper chamberportion 1603.

More specifically, the lower chamber portion 1602 of the vapordeposition chamber 1601 had an outer diameter measuring about 4.5 inches(114 mm), a height of about 3.5 inches (89 mm) and a wall thickness ofabout 0.25 inch (6.4 mm). The lower chamber portion 1602 was machinedfrom a piece of Grade AGSX graphite (Union Carbide Corporation, CarbonProduct Division, Cleveland, Ohio). Two securing tabs 1606 contoured tothe shape of the outer chamber of the lower chamber portion 1602 andmeasuring about 1 inch (25 mm) long, about 1 inch (25 mm) wide, andabout 0.25 inch (6.3 mm) thick were attached to the outer surface of thelower chamber portion 1602, along the top and at opposite ends of thelower chamber portion 1602 so as to extend about 0.5 inch (13 mm) beyondthe top of the lower chamber portion 1602.

The upper chamber portion 1603 of the vapor deposition chamber 1601 hadan outer diameter measuring about 4.5 inches (114 mm), a heightmeasuring about 0.5 inch (13 mm), and a wall thickness measuring about0.25 inch (6.4 mm). The upper chamber portion 1603 further included aparent metal vapor trap 1604 which facilitated the communication betweenthe atmosphere of a vacuum furnace with the atmosphere of vapordeposition chamber 1601, while preventing the parent metal vapor fromescaping into the vacuum furnace. The parent metal vapor trap 1604incorporated three communication holes 1618 through and centrallylocated in the top of the upper chamber portion 1603. The communicationholes 1618 had a diameter of about 0.13 inch (3.3 mm). An extendedportion 1620 of the parent metal vapor trap 1604 measured about 2.13inches (54 mm) long, had an outer diameter measuring about 1.5 inches(38 mm), and had a wall thickness of about 0.13 inch (3.3 mm). Theextended portion 1620 was machined from Grade AGSX graphite (UnionCarbide Corporation, Carbon Product Division, Cleveland, Ohio). Severallayers of Grade GH graphite felt material 1621 (Fiber Materials, Inc.,Biddeford, Me.) were placed into the cavity within the extended portion1620 of the parent metal vapor trap 1604. An attachment portion 1619 ofthe parent metal vapor trap 1604, had an outer diameter measuring about1.25 inches (32 mm), a height measuring 0.5 inch (13 mm), and a wallthickness measuring about 0.13 inch (3.3 mm). The lower attachmentportion 1619 was also machined from Grade AGSX graphite (Union CarbideCorporation, Carbon Product Division, Cleveland, Ohio). Holes forreceiving locking pin 1623, and having an about 0.13 inch (3.3 mm)diameter, were drilled through both the extended portion 1620 and theattachment portion 1619 of the parent metal vapor trap 1604. The parentmetal vapor trap 1604 was completed by fastening, with graphite dowels,the attachment portion 1619 of the parent metal vapor trap 1604 to theupper chamber portion 1603.

The slotted parent metal support member 1608 was machined from GradeAGSX graphite (Union Carbide Corporation, Carbon Products Division,Cleveland, Ohio). The parent metal support member 1608 had an outerdiameter measuring about 3 inches (76 mm), a height measuring about 2.75inches (70 mm) and a wall thickness measuring about 0.25 inch (6.4 mm).The slotted parent metal support member 1608 further comprised an arrayof holes 1611 through its bottom, each hole having a diameter measuringabout 0.13 inch (3.3 mm), forty-three slots 1616 each measuring about0.08 inches wide and about 2.5 inches (mm) along the perimeter, alocater pin 1609 having a diameter measuring about 0.38 inch (9.7 mm)and support pins 1610 each having a diameter measuring about 0.13 (3.3mm). The distance between the outer surface of the slotted parent metalsupport member 1608 and the inner surface of the lower chamber portion1602 of the deposition chamber 1601 was about 0.5 inch (13 mm). Theslotted parent metal support member 1608 provided a means for supportingsolid parent metal while at an elevated temperature, which assists inproviding a sufficient amount of a parent metal vapor during theprocess.

The sample support rack 1613 was attached to the parent metal supportmember 1608 by eight support rods 1612 (only two are depicted in FIG.16a). The sample support rack 1613, machined from Grade AGSX graphite(Union Carbide Corporation, Carbon Products Division, Cleveland, Ohio),had an outer diameter measuring about 2.5 inches (64 mm), a heightmeasuring about 0.25 inch (6.3 mm) and a wall thickness of about 0.25inch (6.4 mm). The support rods 1612, machined from Grade AGSX graphite(Union Carbide Corporation, Carbon Products Division, Cleveland, Ohio),measured about 1 inch (25 mm) long and had a diameter measuring about0.13 (3.3

Prior to aligning the upper chamber portion 1603 of the vapor depositionchamber 1601 with the lower chamber portion 1602 of the vapor depositionchamber 1601, a graphite crucible containing about 119 grams of a parentmetal comprising -5 mesh, +20 mesh (particle diameter from about 850microns to about 4000 microns) titanium metal sponge (Micron Metals,Inc., Salt Lake City, Utah) was placed into the lower chamber portionand on the sample rack 1613. The vapor deposition chamber 1601,containing the parent metal powder in the graphite crucible, was thenplaced into a vacuum furnace and the vacuum furnace door was closed. Thevacuum furnace was then evacuated to a pressure of about 0.2 millitorr.After about 50 minutes at a pressure of about 0.2 millitorr, the vacuumfurnace and its contents were heated to about 1900° C. at about 750° C.per hour while maintaining a pressure of about 0.2 millitorr. Afterabout 2 hours at about 1900° C., with a pressure of about 0.2 millitorr,the vacuum furnace and its contents were cooled at about 900° C. perhour to about 1000° C. while maintaining a pressure of about 0.2millitorr. The vacuum furnace and its contents were then cooled fromabout 1000° C. to about room temperature at about 125° C. per hour whilemaintaining a pressure of about 0.2 millitorr. After replenishing thetitanium parent metal, the processing was repeated twice. At about roomtemperature, the graphite crucible containing the residual titaniumparent metal was removed from the deposition chamber 1601.

Hafnium parent metal sponge 1617 having a size of about -1/4 mesh, +20mesh (particle diameter from about 850 microns to about 6300 microns,Teledyne Wah Chang, Albany, Albany, Oreg.) weighing about 1200 grams wasthen placed into the space between the inner surface of the lowerchamber portion 1602 and the outer surface of the slotted parent metalsupport member 1608.

After sanding the surfaces with 1200 grit (average particle diameter ofabout 4 microns) silicon carbide paper, two graphite substrate coupons1615 (only one is depicted in FIG. 16) comprised of grade AXZ-5Qgraphite (Poco Graphite, Inc., Decature, Tex.) and measuring about Iinch (25 mm) square and about 0.13 inch (3.3 mm) thick, were cleaned forabout 15 minutes in an ultrasonically agitated bath comprising acetoneand were dried in an air oven set at about 120° C. for about 0.25 hours(i.e., until weight losses due to heating at about 120° C. substantiallyceased). After drying substantially completely, the graphite substratecoupons 1615 were placed on a graphite support tray 1614 so that a facemeasuring about 1 inch (25 mm) by about 0.13 inch (3.3 mm) contacted thegraphite support tray. The graphite support tray 1614, which measuredabout 0.045 inch (1.1 mm) thick, with the graphite substrate coupons1615 was then placed on the support frame 1613 within the lower chamberportion 1602.

The upper chamber portion 1603 of the vapor deposition chamber 1601 wasagain placed onto and aligned with the lower chamber portion 1602 of thedeposition chamber 1601. The vapor deposition chamber 1601 and itscontents were then placed into a vacuum furnace and the vacuum furnacedoor was closed. The vacuum furnace was then evacuated to a pressure ofabout 0.2 millitorr. After about 50 minutes at a pressure of about 0.2millitorr, the vacuum furnace and its contents were heated to about1000° C. at about 750° C. per hour while maintaining a pressure of lessthan about 60 millitorr. At about 1000° C., the pressure within thevacuum furnace was allowed to increase to a pressure range between about60 millitorr and about 250 millitorr and the vacuum furnace and itscontents were heated from about 1000° C. to about 2000° C. at about 750°C. per hour. After about 5 hours at about 2000° C., with a pressureranging from about 60 millitorr to about 250 millitorr, the vacuumfurnace and its contents were cooled at about 1000° C. per hour to about1000° C. while maintaining a pressure ranging from about 60 millitorr toabout 250 millitorr. The vacuum furnace and its contents were thencooled from about 1000° C. to about room temperature at about 125° C.per hour while maintaining a pressure ranging from about 60 millitorr toabout 250 millitorr.

At about room temperature, the vacuum furnace door was opened, the vapordeposition chamber 1601 was removed from the furnace, disassembled andthe two graphite substrate coupons 1615 were removed from the lowerchamber portion 1602 of the vapor position chamber 1601. It was notedthat the hafnium sponge material had not melted to any significantextent. Further, it was noted that a light gray metallic finish coatedthe surface of the graphite substrate coupons 1615. One of the graphitesubstrate coupons was intentionally fractured and its surface wasexamined using an electron microscope. The results of the examinationindicated that a coating measuring about 21 microns had formed. Aportion of the coating was subjected to x-ray diffraction analysis,which indicated that the constituents in the area comprising the coatingincluded, among other phases, hafnium carbide. Furthermore, one of thegraphite substrate coupons was cut, mounted and polished formetallographic examination. FIG. 16b is a photomicrograph taken at amagnification of about 200× of the reaction product coating 51 on thegraphite substrate 52.

Thus, this Example generally demonstrates that a parent metal source maycomprise a solid parent metal having a substantial vapor pressure underthe operating conditions of the invention. Further this Examplespecifically demonstrates that a hafnium carbide composite can be formedaccording to the methods of the present invention.

EXAMPLE 21

The following Example demonstrates a method for forming a reactionproduct coating on a molybdenum substrate by reacting a parent metalvapor with a molybdenum substrate coupon at an elevated temperature.Specifically, this Example demonstrates a method for forming amolybdenum silicide coating on a molybdenum substrate coupon by reactinga parent metal vapor comprising silicon with the molybdenum substratecoupon at an elevated temperature.

The three molybdenum substrate coupon rods used in this Example wereobtained from Schwarzkopf Development Corporation, Holliston, Mass., andhad a purity of about 99.95 weight percent molybdenum. Furthermore, eachof the molybdenum substrate coupons had a diameter measuring about 0.5inch (13 mm) and a length measuring about 2.0 inches (51 mm). Each ofthe molybdenum substrate coupons was prepared for coating by placing thecoupons in an ultrasonic bath for about 15 minutes, said bath containinga solution comprising by weight about 50% ethanol and about 50%deionized water. After the molybdenum substrate coupons were removedfrom the ultrasonic bath, the molybdenum substrate coupons were dried inan air at about room temperature for about five minutes. The molybdenumsubstrate coupons were then placed into an oven, set at about 120° C.and the weight was monitored until there was substantially no weightchange. Typically, the molybdenum substrate coupons exhibited no weightchange after about 7 minutes at about 120° C. in the oven. After dryingsubstantially completely, the molybdenum substrate coupons were placedon substrate support rods within the lower chamber portion of a vapordeposition chamber substantially the same as that described in Example10, except that a parent metal powder comprising titanium parent metalwas replaced with particulate silicon parent metal.

The upper chamber portion of the vapor deposition chamber was placedonto and aligned with the lower chamber portion of the depositionchamber. The vapor deposition chamber and its contents were then placedinto a vacuum furnace, and the vacuum furnace door was closed. Thevacuum furnace was then evacuated to a pressure of about 0.2 millitorr.After about 50 minutes at a pressure of about 0.2 millitorr, the vacuumfurnace and its contents were heated to about 1500° C. at about 500° C.per hour while maintaining a pressure of about 0.2 millitorr. Afterabout 2 hours at about 1500° C. with a pressure of about 0.2 millitorr,the vacuum furnace and its contents were cooled to about roomtemperature at a rate of about 500° C. per hour while maintaining apressure of about 0.2 millitorr.

At about room temperature the vacuum furnace door was opened, the vapordeposition chamber was removed from the furnace, disassembled, and themolybdenum substrate coupons were removed from the lower chamber portionof the vapor deposition chamber. It was noted that the color of thesurface of the molybdenum substrate coupons had changed from silver todark gray by subjecting the surfaces to a silicon parent metal vaporcloud according to the method of the Example. Further, the molybdenumsubstrate coupons exhibited a weight change of about 0.5, 0.48, and 0.48grams, respectively, and an increase in diameter of about 0.007, 0.006,and 0.006 inches, respectively. The increase in diameter of themolybdenum substrate coupons and the change in color of the molybdenumsubstrate coupons suggested that molybdenum silicide had formed on thesurface of the molybdenum substrate coupons. Furthermore, one of themolybdenum substrate coupons was cross sectioned, mounted, and polishedfor metallographic examination using an optical microscope. FIG. 17 is aphotomicrograph taken at about 200× of the composite coating 51 on themolybdenum substrate 52.

Thus, this Example demonstrates that a reaction product coating can beformed on a molybdenum substrate coupon by subjecting the substrate to aparent metal vapor cloud comprised of silicon metal vapor.

EXAMPLE 22

The following Example demonstrates a method for forming a reactionproduct coating on a graphite substrate by heating the graphitesubstrate in the presence of at least two sources of parent metal vaporhaving different chemical compositions to permit reaction between thedifferent parent metal vapors and the substrate and/or any formedreaction products. Specifically, this Example demonstrates a method forco-reacting at least a silicon parent metal vapor and a titanium parentmetal vapor with a graphite substrate coupon to form at least onereaction product coating.

The method of Example 3 was substantially repeated except that the onegraphite parent metal source tray was replaced with two, each having anouter diameter of about 2 inches and a wall thickness of about 0.25inches (6.3 mm). A first parent metal source tray had a height of about1 inch (25 mm). In addition, from the top of the first parent metalsource tray extended four support legs, each having a height of about0.5 inch (33 mm), which permitted the parent metal from within thisfirst source tray to communicate with the atmosphere of the vapordeposition chamber while supporting a second parent metal source tray.The second parent metal source tray had a height of about 1 inch (25mm). The first parent metal source tray was filled with a parent metalcomprising silicon weighing about 45 grams. The second parent metalsource tray was filled with a parent metal comprising titanium, whichwas the same titanium as that described in Example 1, and weighing about45 grams. The first and second parent metal source trays were placedinto the bottom of the lower chamber portion of the deposition chamber.Two substrate coupons comprising Grade AXZ-5Q graphite (Poco Graphite,Inc., Decature, Tex.), each measuring about 1 inch (25 mm) square andabout 0.13 inch (3.3 mm) thick, were prepared substantially according tothe method of Example 3, except that no boron carbide was placed on thesurface of the graphite substrate coupons. The graphite substratecoupons were then placed on the support rods within the lower chamberportion and the vapor deposition chamber was assembled to form a lay-up.

The lay-up and its contents were then placed into a vacuum furnace, andthe vacuum furnace door was closed. The vacuum furnace was thenevacuated to a pressure of about 0.2 millitorr. After about 50 minutesat about 0.2 millitorr, the vacuum furnace and its contents were heatedto about 500° C. at about 250° C. per hour while maintaining a pressureof less than about 60 millitorr. The vacuum furnace was then heated fromabout 500° C. to about 1000° C. at about 750° C. per hour whilemaintaining a pressure of less than about 60 millitorr. At about 1000°C., the pressure within the vacuum furnace was allowed to increase to apressure ranging between about 60 millitorr to about 250 millitorr, andthe vacuum furnace and its contents were heated from about 1000° C. toabout 1900° C. at about 750° C. per hour. After about 2 hours at about1900° C. with a pressure ranging from about 60 millitorr to about 250millitorr, the vacuum furnace and its contents were cooled at about 900°C. per hour to about 1000° C. while maintaining a pressure ranging fromabout 60 millitorr to about 250 millitorr. Then the vacuum furnace andits contents were cooled from about 1000° C. to about room temperatureat about 125° C. per hour while maintaining a pressure ranging fromabout 60 millitorr to about 250 millitorr. At about room temperature,the vacuum pump was turned off, the vacuum furnace was allowed to adjustto atmospheric pressure and the lay-up and its contents were removedfrom the furnace. After the lay-up was disassembled, the graphitesubstrate coupons were removed from the vapor deposition chamber and itwas noted that the appearance of the surface of the graphite substratecoupons had changed.

Thus, this Example demonstrates that a reaction product coating can beformed on the surface of graphite substrate by subjecting the substrateto a parent metal vapor cloud comprising at least two parent metals.

EXAMPLE 23

The following Example demonstrates a method for forming a reactionproduct coating on a graphite substrate by applying to the surface of agraphite substrate a first layer of material comprising a solid oxidant,then a second layer of material comprising a parent metal powder andheating the coated graphite substrate in the presence of a parent metalvapor to permit the formation of reaction product due to a reactionbetween the parent metal powder and/or the parent metal vapor with thesolid oxidant, and/or a reaction between the parent metal powder and/orthe parent metal vapor with the graphite substrate and/or reactionbetween formed or forming reaction product(s). More specifically, thefollowing Example demonstrates a method for forming a composite coatingcomprising zirconium carbide and zirconium boride on a graphitesubstrate by applying a first layer comprising boron carbide powder, asecond layer comprising a zirconium parent metal powder, and heating thepowder-covered graphite substrate in the presence of a zirconium parentmetal vapor to permit the reaction between the zirconium parent metalpowder, the boron carbide, and the zirconium parent metal vapor and/orthe graphite substrate.

                                      TABLE IX                                    __________________________________________________________________________                             Total                                                                         # of 1000 grit B.sub.4 C                                                                      -50 Mesh Zr Powder                       Graphite Grade Sample                                                                              Similar                                                                            Weight                                                                             Thickness                                                                           Weight                                                                             Thickness                                                                           Zr/B.sub.4 C              Sample                                                                            and Source     Dimension                                                                           Samples                                                                            (grams)                                                                            (inches)                                                                            (grams)                                                                            (inches)                                                                            Ratio                     __________________________________________________________________________    RUN NO. 1                                                                     AX  AXF-5Q, Poco Graphite Inc.,                                                                        4    0.56 0.015 5.6  0.168 10                            Decature, TX                                                              AY  AGSX, Union Carbide, Carbon                                                                        3    0.28 0.013 2.8  0.111 10                            Products Division, Cleveland,                                                 OH                                                                        AZ  ATJ, Union Carbide, Carbon                                                                         3    0.25 0.013 2.5  0.106 10                            Products Division, Cleveland,                                                 OH                                                                        RUN NO. 2                                                                     BA  AXF-5Q, Poco Graphite Inc.,                                                                        4    0.81 0.001 8.1  0.061 10                            Decature, TX                                                              BB  ISO-88, TTAmerica,   3    0.12 0.006 1.2  0.042 10                            Portland, OR                                                              __________________________________________________________________________

Table IX summarizes the parameters for two runs that demonstrate theformation of a ceramic composite coating comprising zirconium carbideand zirconium boride on various graphite substrates. Specifically, TableIX contains the parameters used for forming composite coatingscomprising zirconium carbide and zirconium boride on Grade AXF-5Qgraphite (Poco Graphite Inc., Decature, Tex.), Grade AGXS graphite(Union Carbide Corporation, Carbon Products Division, Cleveland, Ohio),Grade ATJ graphite (Union Carbide Corporation, Carbon Products Division,Cleveland, Ohio), and Grade IS0-88 graphite (TTAmerica, Portland, Oreg.)using a 1000 grit (average particle diameter of about 5 μm) boroncarbide powder and -50 mesh (particle diameter less than about 297 μm)zirconium parent metal. Additionally, Table IX shows the amount of boroncarbide powder and zirconium parent metal powder applied to a particulargrade of substrate coupon, the thickness at which these powders wereapplied and the weight ratio of zirconium parent metal powder to boroncarbide powder applied to the substrates. Run No. 1 included a total offour samples similar to Sample AX, three samples similar to Sample AY,and three samples similar to Sample AZ for a total of 10 samples,whereas Run No. 2 included four samples similar to Sample BA and threesamples similar to Sample BB for a total of seven samples.

Each of Samples AX through BB were prepared by the following method.After the Samples were cut to the desired dimensions, they were immersedin an ultrasonic bath comprising ethanol. Once removed from the ethanolbath, the samples were placed into an air oven set at about 120° C. forabout 20 minutes, removed from the oven and then allowed to cool toabout room temperature.

At room temperature, a mixture comprising by weight about 40% TETRABOR®1000 grit (average particle diameter of about 5 microns) boron carbide(ESK Engineered Ceramics, New Cannan, Conn.), about 30% deionized water,about 10% ELMER's® polyvinyl acetate professional carpenters wood glue(Borden Chemical, Inc., Columbus, Ohio), and about 20% ethanol wassprayed onto the surfaces of the graphite substrate coupons. An airbrush (Model 150, Badger, Franklin Park, Ill.) set at 30 psi was used toapply the mixture. The graphite substrate coupons were then allowed toair dry. This procedure was repeated five times after which the boroncarbide coated graphite substrate coupons were placed into an air ovenset at about 45° C. for about 20 minutes. The boron carbide coatedgraphite substrate coupons were then weighed and the coating thicknessmeasured.

The boron carbide coated graphite substrate coupons were then sprayedwith a solution comprising by weight about 50% deionized water, about330% ethanol alcohol, and about 17% ELMER'S® polyvinyl acetateprofessional carpenters wood glue (Borden Chemical, Inc., Columbus,Ohio). The airbrush described above, and set at a pressure of about 10lbs per square inch, was used to apply the solution. After the boroncarbide coated substrate was wet, the -50 mesh zirconium powder wassprinkled over and was applied to each surface. Then the zirconiumpowder boron carbide substrate was resprayed with the solution. This wasrepeated until all the zirconium parent metal powder, as shown in TableIX, was applied to the surface of the boron carbide coated substrates.The substrates were then placed into an oven, set at about 45° C. forabout 20 minutes. After drying, the coated graphite substrate couponswere weighed and the coating thickness measured.

The zirconium parent metal, boron carbide powder coated substrates werethen placed into a vapor deposition chamber substantially the same asthat described in Example 10 except that the parent metal in the parentmetal source trays comprise zirconium sponge material (WesternZirconium, Ogden, Utah) having a diameter ranging from about 0.33 inch(0.84 mm) to about 0.25 inch (6.4 mm) to form a lay-up.

The lay-up comprising the vapor deposition chamber and its contents wasthen placed into a vacuum furnace and the vacuum furnace door wasclosed. The vacuum furnace was evacuated to a pressure of about 0.2millitorr. After about 50 minutes at a pressure of about 0.2 millitorr,the vacuum furnace and its contents were heated from about roomtemperature to about 2000° C. at a rate of about 700° C. per hour whilemaintaining a pressure of about 0.2 millitorr. After about 2 hours atabout 2000° C. with a pressure of about 0.2 millitorr, the furnace andits contents were cooled at about 1000° C. per hour to about 1000° C.while maintaining a pressure of about 0.2 millitorr. The vacuum furnaceand its contents were then cooled from about 1000° C. to about roomtemperature at about 125° C. per hour while maintaining a pressure ofabout 0.2 millitorr. At about room temperature, the vacuum furnace doorwas opened, the vapor deposition chamber was removed from the furnace,disassembled, and the graphite substrate coupons were removed from thelower chamber portion of the vapor deposition chamber. It was noted thatthe powdered coating on the graphite substrate coupon had becomeintegral with the graphite substrate coupons. Sample AY was then crosssectioned, polished, and mounted for metallographic examination in anelectron microscope. FIG. 18a is a photomicrograph taken at about 50× inthe electron microscope using the backscattered electron mode showingthe ceramic composite coating 51 on the graphite substrate coupon 52.Additionally, FIG. 18a shows that some of the parent metal infiltratedinto the pores of the graphite substrate coupon. FIG. 18b is aphotomicrograph taken at about 200× corresponding to Sample AY showingthe platelet structure of the resultant ceramic composite coating formedon the graphite substrate coupon. Additionally, FIG. 18c is aphotomicrograph taken at about 200× in the electron microscope using thebackscattered electron mode showing the ceramic composite coating formedon Sample BB of this Example.

Thus, this Example demonstrates that a ceramic composite coating can beformed on a substrate coupon by placing a first layer of a solid oxidantonto the surface of the graphite substrate coupon, then placing a secondlayer of a parent metal powder onto the substrate coupon and subjectingthe powder coated graphite substrate coupon to a parent metal vapor toeffect a reaction between parent metal powder, the vapor parent metal,solid oxidant and/or the graphite substrate.

EXAMPLE 24

The following Example demonstrates, among other things, a method forforming a reaction product on a graphite substrate coupon by reacting aparent metal vapor with a graphite substrate coupon at an elevatedtemperature. Specifically, the following Example further demonstrates amethod of forming a hafnium carbide composite coating on a graphitesubstrate by the method of the present invention.

The method of Example 20 was substantially repeated except that theamount of hafnium parent metal used was about 1070 grams. Furthermore,after the vapor deposition chamber 1601 and its contents were placedinto the vacuum furnace, the vacuum furnace was evacuated to a pressureof about 0.2 millitorr. After about 50 minutes at a pressure of about0.2 millitorr, the vacuum furnace and its contents were heated to about2225° C. at a rate of about 750° C. per hour, while maintaining apressure of less than about 60 millitorr. After about 3 hours at about2225°, with a pressure of about 0.2 millitorr, the vacuum furnace andits contents were cooled to about 1000° C. at about 900° C. per hourwhile maintaining a pressure of about 0.2 millitorr. The vacuum furnaceand its contents were then cooled from about 1000° C. to about roomtemperature at about 125° C. per hour while maintaining a pressure ofabout 0.2 millitorr. At about room temperature, the vacuum furnace doorwas opened, the vapor deposition chamber 1601 was removed from thefurnace, disassembled and two graphite substrate coupons 1615 wereremoved from the lower chamber portion 1602 of the vapor depositionchamber 1601. It was noted that the hafnium sponge material had notmelted to any significant extent. Further, it was noted that a lightgray metallic finish substantially completely coated the surface of thegraphite substrate coupon 1615. One of the graphite substrate couponswas broken and its surface examined using an electron microscope. Theresults of the examination indicated that a coating measuring about 9.5microns had formed. FIG. 19a is a photomicrograph taken at amagnification of about 4000× of the ceramic composite coating 51 on thegraphite substrate 52. The photomicrograph was taken in an electronmicroscope using the secondary electron image mode.

Thus, this Example further demonstrates that a parent metal source maycomprise a solid parent metal having a substantial vapor pressure.Further, this Example demonstrates that a hafnium carbide compositecoating may be formed on the surface of a graphite substrate accordingto the methods of the present invention.

We claim:
 1. A method for forming a self-supporting bodycomprising:providing at least one vapor-phase parent metal; providing asubstrate material which is substantially non-reactive with saidvapor-phase parent metal; coating said substrate material with a solidoxidant-containing material; contacting said at least one vapor-phaseparent metal with at least a portion of said solid oxidant-containingmaterial; and permitting said at least one vapor-phase parent metal andsaid solid oxidant-containing material to form a reaction product on atleast a portion of said solid oxidant-containing material.
 2. The methodof claim 1, wherein said at least one vapor-phase parent metal comprisesat least one metal selected from the group consisting of titanium,zirconium, hafnium, silicon and niobium.
 3. The method of claim 1,wherein said solid oxidant-containing material comprises a carbonaceousmaterial or a molybdenum-containing material.
 4. The method of claim 1,wherein said solid oxidant-containing material further comprises atleast one filler located on at least one surface of said solidoxidant-containing material and said reaction product at least partiallyembeds said at least one filler.
 5. The method of claim 3, wherein saidreaction product at least partially embeds said filler.
 6. The method ofclaim 1, wherein said solid oxidant-containing material comprises afirst solid oxidant-containing material having at least a portion of atleast one surface coated with a second solid oxidant-containingmaterial.
 7. The method of claim 1, wherein at least a portion of saidsolid oxidant-containing material is coated with a powdered parentmetal.
 8. The method of claim 1, wherein said solid oxidant-containingmaterial is substantially completely converted to reaction product. 9.The method of claim 1, wherein said solid oxidant-containing materialcomprises a carbon-carbon composite substrate.
 10. A self-supportingcomposite body comprising:a solid oxidant-containing material comprisinga molybdenum-containing material; and a coating comprising at least onemolybdenum silicide material covering at least a portion of at least onesurface of said molybdenum-containing material.
 11. A self-supportingcomposite body comprising a substrate material which is substantiallynon-reactive with the vapor-phase of metals selected from the groupconsisting of titanium, zirconium, hafnium, niobium and silicon; a solidoxidant-containing material comprising a carbon-containing materialwhich covers at least a portion of said substrate material; and acoating comprising at least one material selected from the groupconsisting of titanium carbide, zirconium carbide, hafnium carbide,niobium carbide, silicon carbide and mixtures thereof covering at leasta portion of at least one surface of said carbon-containing material.12. The self-supporting composite body of claim 10, wherein said coatingfurther comprises at least one filler.
 13. The self-supporting compositebody of claim 11, wherein said coating further comprises at least onefiller.
 14. The self-supporting composite body of claim 10, furthercomprising a substrate material, wherein said substrate material atleast partially contacts said solid oxidant-containing material.
 15. Theself-supporting composite body of claim 11, wherein at least a portionof said coating comprises at least one material selected from the groupconsisting of titanium diboride, hafnium diboride, and zirconiumdiboride.
 16. The self-supporting composite body of claim 13, wherein atleast a portion of said coating further comprises at least one materialselected from the group consisting of titanium diboride, hafniumdiboride, and zirconium diboride.
 17. A setup for performing a processof directed metal oxidation of a solid oxidant-containing material witha parent metal vapor to form self-supporting bodies, havingsubstantially homogeneous compositions, graded compositions, andmacrocomposite bodies, said setup comprising:a chamber comprising: (a)at least one material which does not adversely react with said parentmetal vapor and said solid oxidant-containing materials; (b) acommunication means for facilitating the communication between anatmosphere external to said chamber with an atmosphere within saidchamber and preventing said parent metal vapor from escaping from saidchamber and into said atmosphere external to said chamber, saidcommunication means located in at least a portion of said chamber; (c) aparent metal providing means for introducing said parent metal vaporinto said chamber, said introducing means being located external to orwithin said chamber; and (d) a supporting means for supporting saidsolid oxidant-containing material, said supporting means being at leastpartially located within said chamber.
 18. The setup of claim 17,wherein said at least one material comprises graphite.
 19. The setup ofclaim 17, wherein said communications means comprises a parent metalvapor.
 20. The setup of claim 19, wherein said parent metal vapor trapcomprises at least one of a graphite felt-and a graphite fiber board.21. The setup of claim 17, wherein said supporting means comprises atleast one body selected from the group consisting of rods and plates.22. The method of claim 1, wherein said reaction product is directlybonded to said substrate.
 23. The method of claim 1, wherein at least aportion of said solid oxidant-containing material remains unreacted, andsaid reaction product is integrally bonded to said substrate throughsaid remaining solid oxidant-containing material.